Resist composition and method of forming resist pattern

ABSTRACT

A resist composition including a base component and an acid generator component, the base component including a resin component having a structural unit (a0) represented by general formula (a0) shown below, and the acid generator component containing at least one of a compound (b-1), a compound (b-2) and a compound (b-3) represented by general formula (b-3) shown below in which Wa represents a divalent aromatic hydrocarbon group; Ra 00  represents an acid dissociable group; R 101 , R 104  and R 106  each independently represents a hydrocarbon group containing an aromatic ring; R 105 , R 107  and R 108  each independently represents a cyclic group, a chain alkyl group which may have a substituent or a chain alkenyl group; R 102  represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbon atoms and M′ m+  represents an m-valent onium cation.

TECHNICAL FIELD

The present invention relates to a resist composition and a method offorming a resist pattern.

Priority is claimed on Japanese Patent Application No. 2018-115625,filed Jun. 18, 2018, the content of which is incorporated herein byreference.

DESCRIPTION OF RELATED ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure, followed by development, therebyforming a resist pattern having a predetermined shape on the resistfilm. A resist material in which the exposed portions of the resist filmbecome soluble in a developing solution is called a positive-type, and aresist material in which the exposed portions of the resist film becomeinsoluble in a developing solution is called a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter (energy higher) thanthese excimer lasers, such as electron beam (EB), extreme ultravioletradiation (EUV), and X ray.

In addition, currently, as the resist material in EUV lithography and EBlithography, chemically amplified resists proposed for KrF excimer laserand ArF excimer laser have been generally used since such chemicallyamplified resists exhibit excellent lithography properties, such assensitivity to EUV and EB, and resolution sufficient to form a fineresist pattern as a target. In particular, chemically amplified resistcontaining an acrylic resin as the base material are known to beadvantageous in such lithography properties.

Regarding the resist material, particularly in EUV exposure, aciddiffusion control was a problem. For controlling acid diffusion, theanion structure of the acid generator is generally changed. Acidgenerators having an anion structure with a short acid diffusion lengthare already applied.

For further controlling acid diffusion, methods in which designs ofpolymeric compounds are variously changed have been employed.

For example, Patent Literature 1 describes a resist compositionemploying a polymeric compound having a specific acid dissociablefunctional group, so as to improve the reactivity to acid and solubilityin a developing solution.

Patent Literature 2 describes a resist composition employing a polymericcompound containing a repeating unit having a styrenecarboxylic acidskeleton in which the hydrogen atom of the hydroxy group in the carboxygroup has been substituted with an acid labile group, so as to suppressdiffusion of acid and improve dissolution contrast and etchingresistance.

PATENT LITERATURE

-   [Patent Literature 1] WO2010/095698-   [Patent Literature 2] Japanese Patent No. 4305637

SUMMARY OF THE INVENTION

As the lithography technique further progresses and the miniaturizationof the resist pattern progresses more and more, for example, a target ofthe lithography performed by electron beams and EUV is to form fineresist patterns of several tens of nanometers. As miniaturization ofpattern progress, improvement will be demanded for resist compositionwith respect to high sensitivity to exposure source and lithographyproperties such as reduced roughness. In order to further improve thelithography properties, there was still room for modifying theformulation of a polymeric compound and an acid generator in a resistcomposition.

The present invention takes the above circumstances into consideration,with an object of providing a resist composition which exhibits goodlithography properties, and a method of forming a resist pattern usingthe resist composition.

As a result of the studies of the present inventors, they have foundthat roughness of a resist pattern may be improved by controlling thediffusion of acid generated upon exposure to unexposed portions of thepattern. Further, the present inventors have found that, by enhancingthe interaction between the base resin of the resist and the acidgenerator, diffusion of acid may be suppressed. The present inventionhave been completed based on these findings.

A first aspect of the present invention is a resist composition whichgenerates acid upon exposure and exhibits changed solubility in adeveloping solution under action of acid, the resist compositionincluding a base component (A) which exhibits changed solubility in adeveloping solution under action of acid and an acid generator component(B) which generates acid upon exposure, the base component (A) includinga resin component (A1) having a structural unit (a0) represented bygeneral formula (a0) shown below, and the acid generator component (B)containing at least one member selected from the group consisting of acompound (b-1) represented by general formula (b-1) shown below, acompound (b-2) represented by general formula (b-2) shown below and acompound (b-3) represented by general formula (b-3) shown below.

In the formula, R⁰ represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;Va^(x0) represents a single bond or a divalent linking group; Warepresents a divalent aromatic hydrocarbon group which may have asubstituent; Va⁰ represents a divalent hydrocarbon group which may havean ether bond; n_(a0) represents an integer of 0 to 2; and Ra⁰⁰represents an acid dissociable group.

In the formulae, R¹⁰¹, R¹⁰⁴ and R¹⁰⁶ each independently represents ahydrocarbon group containing an aromatic ring which may have asubstituent; R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent; R¹⁰²represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbonatoms; Y¹⁰¹ represents a single bond or a divalent linking groupcontaining an oxygen atom;

V¹⁰¹ to V¹⁰³ each independently represents a single bond, an alkylenegroup or a fluorinated alkylene group; L¹⁰¹ and L¹⁰² each independentlyrepresents a single bond or an oxygen atom; L¹⁰³ to L¹⁰⁵ eachindependently represents a single bond, —CO— or —SO₂—; m represents aninteger of 1 or more; and M′^(m+) represents an m-valent onium cation.

A second aspect of the present invention is a method of forming a resistpattern, including: using a resist composition according to the firstaspect to form a resist film on a substrate, subjecting the resist filmto exposure, and subjecting the exposed resist film to developing toform a resist pattern.

According to the present invention, there are provided a resistcomposition which exhibits excellent lithography properties, and amethod of forming a resist pattern using the resist composition.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

The expression “may have a substituent” means that a case where ahydrogen atom (—H) is substituted with a monovalent group, or a casewhere a methylene (—CH₂—) group is substituted with a divalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent(R^(α0)) that substitutes the hydrogen atom bonded to the carbon atom onthe α-position is an atom other than hydrogen or a group, and examplesthereof include an alkyl group of 1 to 5 carbon atoms and a halogenatedalkyl group of 1 to 5 carbon atoms. Further, an acrylate ester havingthe hydrogen atom bonded to the carbon atom on the α-positionsubstituted with a substituent (R^(α0)) in which the substituent hasbeen substituted with a substituent containing an ester bond (e.g., anitaconic acid diester), or an acrylic acid having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent (R^(α0)) in which the substituent has been substituted witha hydroxyalkylgroup or a group in which the hydroxy group within ahydroxyalkyl group has been modified (e.g., α-hydroxyalkyl acrylateester) may be mentioned as an acrylate ester having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent. A carbon atom on the α-position of an acrylate ester refersto the carbon atom bonded to the carbonyl group, unless specifiedotherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters are collectivelyreferred to as “(α-substituted) acrylate ester”. Hereafter, an acrylateester having the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is sometimes referred to as“α-substituted acrylate ester”. Further, acrylic acid and α-substitutedacrylic acids are collectively referred to as “(α-substituted) acrylicacid”.

A “structural unit derived from acrylamide” refers to a structural unitthat is formed by the cleavage of the ethylenic double bond ofacrylamide.

The acrylamide may have the hydrogen atom bonded to the carbon atom onthe α-position substituted with a substituent, and may have either orboth terminal hydrogen atoms on the amino group of acrylamidesubstituted with a substituent. A carbon atom on the α-position of anacrylamide refers to the carbon atom bonded to the carbonyl group,unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof acrylamide, the same substituents as those described above for thesubstituent (R^(α0)) on the α-position of the aforementioned α-positionof the aforementioned α-substituted acrylate ester may be mentioned.

A “structural unit derived from hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond ofhydroxystyrene. A “structural unit derived from a hydroxystyrenederivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxy grouphas been substituted with an organic group and may have the hydrogenatom on the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxy group bondedto the benzene ring and may have the hydrogen atom on the α-positionsubstituted with a substituent. Here, the α-position (carbon atom on theα-position) refers to the carbon atom having the benzene ring bondedthereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent on the α-position of the aforementioned α-substitutedacrylate ester may be mentioned.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Examples of thederivatives thereof include benzoic acid in which the hydrogen atom ofthe carboxy group has been substituted with an organic group and mayhave the hydrogen atom on the α-position substituted with a substituent;and benzoic acid which has a substituent other than a hydroxy group anda carboxy group bonded to the benzene ring and may have the hydrogenatom on the α-position substituted with a substituent. Here, theα-position (carbon atom on the α-position) refers to the carbon atomhaving the benzene ring bonded thereto, unless specified otherwise.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxy group. The number of hydroxy groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

In the present specification and claims, some structures represented bychemical formulae may have an asymmetric carbon, such that an enantiomeror a diastereomer may be present. In such a case, the one formularepresents all isomers. The isomers may be used individually, or in theform of a mixture.

(Resist Composition)

The resist composition of the present embodiment generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid.

The resist composition contains a base component (A) (hereafter,sometimes referred to as “base component (A)”) which exhibits changedsolubility in a developing solution.

When a resist film is formed using the resist composition according tothe present embodiment, and the resist film is selectively exposed, acidis generated at exposed portions of the resist film, and the solubilityof the component (A) in a developing solution is changed by the actionof the acid. On the other hand, at unexposed portions of the resistfilm, the solubility of the component (A) in a developing solution isunchanged. As a result, difference is generated between the exposedportions of the resist film and the unexposed portions of the resistfilm in terms of solubility in a developing solution. Therefore, bysubjecting the resist film to development, the exposed portions of theresist film are dissolved and removed to form a positive-tone resistpattern in the case of a positive resist, whereas the unexposed portionsof the resist film are dissolved and removed to form a negative-toneresist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsof the resist film is called a positive resist composition, and a resistcomposition which forms a negative resist pattern by dissolving andremoving the unexposed portions of the resist film is called a negativeresist composition.

The resist composition of the present embodiment may be either apositive resist composition or a negative resist composition.

Further, in the present embodiment, the resist composition may beapplied to an alkali developing process using an alkali developingsolution in the developing treatment, or a solvent developing processusing a developing solution containing an organic solvent (organicdeveloping solution) in the developing treatment, and preferably asolvent developing process.

That is, the resist composition of the present embodiment is preferablya resist composition which forms a positive pattern in an alkalideveloping process (i.e, a positive resist compound for alkalideveloping process) or a resist composition which forms a negativepattern in a solvent developing process (i.e., a negative type resistcomposition for solvent developing process).

The resist composition of the present embodiment is capable ofgenerating acid upon exposure. The acid may be generated from thecomponent (A) upon exposure, or the acid may be generated from anadditive component other than the component (A) upon exposure.

In the present embodiment, the resist composition may be a resistcomposition (1) containing an acid generator component (B) whichgenerates acid upon exposure (hereafter, referred to as “component (B)”;a resist composition (2) in which the component (A) is a component whichgenerates acid upon exposure; or a resist composition (3) in which thecomponent (A) is a component which generates acid upon exposure, andfurther containing an acid generator component (B).

That is, when the resist composition of the present invention is theaforementioned resist composition (2) or (3), the component (A) is a“base component which generates acid upon exposure and exhibits changedsolubility in a developing solution under action of acid”. In the casewhere the component (A) is a base component which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, the component (A1) described later is preferably apolymeric compound which generates acid upon exposure and exhibitschanged solubility in a developing solution under action of acid. As thepolymeric compound, a resin having a structural unit which generatesacid upon exposure may be used.

As the structural unit which generates acid upon exposure, aconventional structural unit may be used.

The resist composition of the present embodiment is most preferably theaforementioned resist composition (1).

<Component (A)>

The component (A) is a base component which exhibits changed solubilityin a developing solution under action of acid.

In the present invention, the term “base component” refers to an organiccompound capable of forming a film, and is preferably an organiccompound having a molecular weight of 500 or more. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a resist pattern of nano level may be easily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “resin” or a “polymer” refers to apolymer having a molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

In the resist composition according to the present embodiment, thecomponent (A) contains a resin component (A1) (hereafter, referred to as“component (A1)”) which exhibits changed solubility in a developingsolution by the action of acid.

As the component (A), at least the component (A1) is used, and apolymeric compound and/or a low molecular weight compound may be used incombination with the component (A1).

<<Component (A1)>>

The component (A1) includes a structural unit (a0) represented bygeneral formula (a0) described later. If desired, the component (A1) mayinclude, in addition to the structural unit (a0), other structural unit.

In the resist composition of the present embodiment, since thestructural unit (a0) contains an acid dissociable group, by using thecomponent (A1), the polarity of the resin component changes before andafter exposure. Therefore, an excellent development contrast may beobtained between exposed portions and unexposed portions of the resistfilm not only in an alkali developing process, but also in a solventdeveloping process.

More specifically, in the case of applying an alkali developing process,the component (A1) is substantially insoluble in an alkali developingsolution prior to exposure, but when acid is generated from thecomponent (B) upon exposure, the action of this acid causes an increasein the polarity of the base component, thereby increasing the solubilityof the component (A1) in an alkali developing solution. Therefore, inthe formation of a resist pattern, by conducting selective exposure of aresist film formed by applying the resist composition to a substrate,the exposed portions of the resist film change from an insoluble stateto a soluble state in an alkali developing solution, whereas theunexposed portions of the resist film remain insoluble in an alkalideveloping solution, and hence, a positive resist pattern is formed byalkali developing.

On the other hand, in the case of a solvent developing process, thecomponent (A1) exhibits high solubility in an organic developingsolution prior to exposure, and when acid is generated from thecomponent (B) upon exposure for example, the polarity of the component(A1) is increased by the action of the generated acid, therebydecreasing the solubility of the component (A1) in an organic developingsolution. Therefore, in the formation of a resist pattern, by conductingselective exposure of a resist film formed by applying the resistcomposition to a substrate, the exposed portions of the resist filmchanges from an soluble state to an insoluble state in an organicdeveloping solution, whereas the unexposed portions of the resist filmremain soluble in an organic developing solution. As a result, byconducting development using an organic developing solution, therebyforming a negative resist pattern.

(Structural Unit (a0)):

The structural unit (a0) is a structural unit represented by generalformula (a0) shown below.

The structural unit (a0) contains an acid decomposable group whichexhibits increased polarity by the action of acid. The term “aciddecomposable group” refers to a group in which at least a part of thebond within the structure thereof is cleaved by the action of an acid.In the structural unit (a0), by the action of acid, the bond between theacid dissociable group Ra⁰⁰ and the oxygen atom (—O—) of the carbonyloxygroup (—C(═O)—O—) adjacent to the acid dissociable group Ra⁰⁰ iscleaved, and a polar group having a high polarity (carboxy group) isgenerated, such that the polarity is increased.

In the formula, R⁰R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;Va^(x0) represents a single bond or a divalent linking group; Warepresents a divalent aromatic hydrocarbon group which may have asubstituent; Va⁰ represents a divalent hydrocarbon group which may havean ether bond; n_(a0) represents an integer of 0 to 2; and Ra⁰⁰represents an acid dissociable group.

In formula (a0), R⁰ represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms.

As the alkyl group of 1 to 5 carbon atoms for R⁰, a linear or branchedalkyl group of 1 to 5 carbon atoms is preferable, and specific examplesthereof include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

Examples of the halogen atom for R⁰ include a fluorine atom, chlorineatom, bromine atom and iodine atom, and a fluorine atom is preferable.

The halogenated alkyl group of 1 to 5 carbon atoms represented by R⁰ isa group in which part or all of the hydrogen atoms of the aforementionedalkyl group of 1 to 5 carbon atoms have been substituted with halogenatoms.

As R⁰, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and interms of industrial availability, a hydrogen atom, a methyl group or afluorine atom is more preferable, and a hydrogen atom is still morepreferable.

In formula (a0), Va^(x0) represents a single bond or a divalent linkinggroup.

The divalent linking group for Va^(x0) is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

Divalent Hydrocarbon Group which May have a Substituent:

Va^(x0) is a divalent linking group which may have a substituent, thehydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group.

Aliphatic Hydrocarbon Group for Va^(x0)

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof may be given.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbonatoms, more preferably 3 to 6, still more preferably 3 or 4, and mostpreferably 3.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing a Ring in the Structure Thereof

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group containing a hetero atomin the ring structure thereof and may have a substituent (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the cyclic aliphatic hydrocarbon group is bondedto the terminal of the aforementioned chain aliphatic hydrocarbon group,and a group in which the cyclic aliphatic group is interposed within theaforementioned linear or branched aliphatic hydrocarbon group, may begiven. As the linear or branched aliphatic hydrocarbon group, the samegroups as those described above may be used.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic aliphatic hydrocarbon group, agroup in which 2 hydrogen atoms have been removed from a monocycloalkaneis preferable. The monocycloalkane preferably has 3 to 6 carbon atoms,and specific examples thereof include cyclopentane and cyclohexane. Asthe polycyclic group, a group in which 2 hydrogen atoms have beenremoved from a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and still more preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

The cyclic aliphatic hydrocarbon group may have part of the carbon atomsconstituting the ring structure thereof substituted with a substituentcontaining a hetero atom. As the substituent containing a hetero atom,—O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group for Va^(x0)

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbonatoms. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ringand a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring or aromatic hetero ring (arylene group orheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (a group in which onehydrogen atom has been removed from the aryl group within theaforementioned arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group, or a heteroarylalkylgroup). The alkylene group which is bonded to the aforementioned arylgroup or heteroaryl group preferably has 1 to 4 carbon atoms, morepreferably 1 or 2 carbon atoms, and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom withinthe aromatic hydrocarbon group may be substituted with a substituent.For example, the hydrogen atom bonded to the aromatic ring within thearomatic hydrocarbon group may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and more preferably a methyl group, an ethyl group, apropyl group, an n-butyl group or a tert-butyl group.

As the alkoxy group, the halogen atom and the halogenated alkyl groupfor the substituent, the same groups as the aforementioned substituentgroups for substituting a hydrogen atom within the cyclic aliphatichydrocarbon group may be used.

Divalent Linking Group Containing a Hetero Atom

In the case where Va^(x0) represents a divalent linking group containinga hetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (may be substituted with a substituent such as an alkylgroup, an acyl group or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by general formula: —Y²¹—O—Y²²—, —Y²¹—O—,—Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—,—Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²²each independently represents a divalent hydrocarbon group which mayhave a substituent, O represents an oxygen atom, and m′ represents aninteger of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group for Ya^(x1).

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m″)—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Among these examples, as Va^(x0), a single bond, an ester bond[—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of any of these groups is preferable, asingle bond or an ester bond [—C(═O)—O—, —O—C(═O)—] is more preferable,and a single bond is still more preferable.

In formula (a0), Wa represents a divalent aromatic hydrocarbon groupwhich may have a substituent.

Examples of the aromatic hydrocarbon group for Wa include a group inwhich two hydrogen atoms have been removed from an aromatic ring. Thearomatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbonatoms. Specific examples of the aromatic ring include an aromatichydrocarbon ring, such as benzene, naphthalene, anthracene orphenanthrene; and an aromatic heterocyclic ring in which part of thecarbon atoms constituting the aromatic hydrocarbon ring has beensubstituted with a heteroatom. Examples of the hetero atom within thearomatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom. Specific examples of the aromatic hetero ring include apyridine ring and a thiophene ring.

Further examples of the aromatic hydrocarbon group for Wa include agroup in which two hydrogen atoms have been removed from an aromaticcompound containing 2 or more aromatic rings (e.g., biphenyl, fluorene,or the like).

Among these examples, as Wa, a group in which two hydrogen atoms havebeen removed from benzene, naphthalene, anthracene or biphenyl ispreferable, a group in which two hydrogen atoms have been removed frombenzene or naphthalene (i.e., a phenylene group or a naphthylene group)is more preferable, and a group in which two hydrogen atoms have beenremoved from benzene (i.e., a phenylene group) is still more preferable.

Examples of substituents for the aromatic hydrocarbon group representedby Wa include a linear or branched alkyl group having 1 to 5 carbonatoms, a halogen atoms, and a linear or branched halogenated alkyl grouphaving 1 to 5 carbon atoms, a halogen atoms.

Examples of linear or branched alkyl groups of 1 to 5 carbon atomsinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, a tert-butyl group, a pentylgroup, an isopentyl group and a neopentyl group. Among these examples, amethyl group is preferable.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is preferable.

The halogenated alkyl group of 1 to 5 carbon atoms represented by R is agroup in which part or all of the hydrogen atoms of the aforementionedalkyl group of 1 to 5 carbon atoms have been substituted with halogenatoms.

In formula (a0), Va^(x1) represents a divalent hydrocarbon group whichmay have an ether bond. The divalent hydrocarbon group for Va^(x1) maybe an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon group forVa^(x1) may be either saturated or unsaturated. In general, thealiphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof may be given.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain aliphatic hydrocarbon group, and a group in whichthe alicyclic group is interposed within the aforementioned linear orbranched aliphatic hydrocarbon group, may be given. The linear orbranched aliphatic hydrocarbon group is the same as defined for theaforementioned linear aliphatic hydrocarbon group or the aforementionedbranched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobomane, tricyclodecane andtetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon group forVa^(x1) is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, morepreferably 5 to 30, still more preferably 5 to 20, still more preferably6 to 15, and most preferably 6 to 10. Here, the number of carbon atomswithin a substituent(s) is not included in the number of carbon atoms ofthe aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In formula (a0), n_(a0) represents an integer of 0 to 2, preferably 0 or1, and more preferably 0.

In formula (a0), Ra⁰⁰ represents an acid dissociable group.

The “acid dissociable group” refers to both (i) a group in which thebond between the acid dissociable group and the adjacent atom is cleavedby the action of acid; and (ii) a group in which one of the bonds iscleaved by the action of acid, and then a decarboxylation reactionoccurs, thereby cleaving the bond between the acid dissociable group andthe adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes, and the solubility in an alkali developingsolution is relatively increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

Examples of the acid dissociable group for Ra⁰⁰ include groups whichhave been proposed as acid dissociable groups for the base resin of aconventional chemically amplified resist composition.

Specific examples of acid dissociable groups for the base resin of aconventional chemically amplified resist composition include“acetal-type acid dissociable group”, “tertiary alkyl ester-type aciddissociable group” and “tertiary alkyloxycarbonyl acid dissociablegroup” described below.

Acetal-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupor hydroxy group as a polar group include the acid dissociable grouprepresented by general formula (a1-r-1) shown below (hereafter, referredto as “acetal-type acid dissociable group”).

In the formula, Ra′¹ and Ra′² represents a hydrogen atom or an alkylgroup; and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′².

In the formula (a1-r-1), it is preferable that at least one of Ra′¹ andRa′² represents a hydrogen atom, and it is more preferable that both ofRa′¹ and Ra′² represent a hydrogen atom.

In the case where Ra′¹ or Ra′² is an alkyl group, as the alkyl group,the same alkyl groups as those described above the for the substituentwhich may be bonded to the carbon atom on the α-position of theaforementioned α-substituted acrylate ester may be mentioned, and analkyl group of 1 to 5 carbon atoms is preferable. Specific examplesinclude linear or branched alkyl groups. Specific examples of the alkylgroup include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group. Ofthese, a methyl group or an ethyl group is preferable, and a methylgroup is particularly preferable.

In formula (a1-r-1), examples of the hydrocarbon group for Ra′³ includea linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples include an isopropyl group, anisobutyl group, a tert-butyl group, an isopentyl group, a neopentylgroup a 1,1-diethylpropyl group and a 2,2-dimethylbutyl group. Amongthese, an isopropyl group is preferable.

In the case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be an aliphatic hydrocarbon group or an aromatichydrocarbon group, and may be polycyclic or monocyclic.

As the monocyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a monocycloalkane is preferable. Themonocycloalkane preferably has 3 to 6 carbon atoms, and specificexamples thereof include cyclopentane and cyclohexane.

As the polycyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a polycycloalkane is preferable, andthe polycyclic group preferably has 7 to 12 carbon atoms. Examples ofthe polycycloalkane include adamantane, norbornane, isobomane,tricyclodecane and tetracyclododecane.

When the monovalent hydrocarbon group for Ra′³ is an aromatichydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon grouphaving at least one aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20, still more preferably 6 to 15,and most preferably 6 to 10.

Examples of the aromatic ring include aromatic hydrocarbon rings, suchas benzene, naphthalene, anthracene and phenanthrene; and aromatichetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.Specific examples of the aromatic hetero ring include a pyridine ring, athiophene ring and a furan ring.

Specific examples of the aromatic hydrocarbon group for Ra′³ include agroup in which one hydrogen atom has been removed from theaforementioned aromatic hydrocarbon ring or aromatic hetero ring (arylgroup or heteroaryl group); a group in which one hydrogen atom has beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof the aforementioned aromatic hydrocarbon ring or aromatic hetero ringhas been substituted with an alkylene group (an arylalkyl group such asa benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethylgroup). The alkylene group bonded to the aforementioned aromatichydrocarbon ring or the aromatic hetero ring preferably has 1 to 4carbon atoms, more preferably 1 or 2 carbon atoms, and most preferably 1carbon atom.

In the case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4 to 7-membered ring, and more preferably a4 to 6-membered ring. Specific examples of the cyclic group includetetrahydropyranyl group and tetrahydrofuranyl group.

In formula (a1-r-1), the hydrocarbon group for Ra′³ is preferably analicyclic hydrocarbon group, more preferably a polycyclic aliphatichydrocarbon group, still more preferably a group in which one hydrogenatom has been removed from adamantane, norbomane, isobomane,tricyclodecane or tetracyclododecane, and most preferably a group inwhich one hydrogen atom has been removed from adamantane.

Tertiary Alkyl Ester-Type Acid Dissociable Group

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented bygeneral formula (a1-r-2) shown below.

Among the acid dissociable groups represented by general formula(a1-r-2), for convenience, a group which is constituted of alkyl groupsis referred to as “tertiary ester-type acid dissociable group”.

In the formula, Ra′⁴ to Ra′⁶ each independently represents a hydrocarbongroup which may have a substituent, provided that Ra′⁵ and Ra′⁶ may bemutually bonded to form a ring.

Examples of the hydrocarbon group (which may have a substituent) forRa′⁴ to Ra′⁶ include a linear or branched alkyl group (a chain alkylgroup), a linear or branched alkenyl group (a chain alkenyl group), or acyclic hydrocarbon group.

The linear alkyl group for Ra′⁴ to Ra′⁶ preferably has 1 to 20 carbonatoms, more preferably 1 to 15 carbon atoms, and still more preferably 1to 10 carbon atoms. Specific examples include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a nonyl group, a decyl group, an undecylgroup, a dodecyl group, a tridecyl group, an isotridecyl group, atetradecyl group, a pentadecyl group, a hexadecyl group, an isohexadecylgroup, a heptadecyl group, an octadecyl group, a nonadecyl group, anicosyl group, a henicosyl group and a docosyl group.

The branched alkyl group for Ra′⁴ to Ra′⁶ preferably has 3 to 20 carbonatoms, more preferably 3 to 15 carbon atoms, and still more preferably 3to 10 carbon atoms. Specific examples include a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group and a 4-methylpentyl group.

The linear or branched alkenyl group for Ra′⁴ to Ra′⁶ preferably has 2to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still morepreferably 2 to 4 carbon atoms, and most preferably 3 carbon atoms.Examples of linear alkenyl groups include a vinyl group, a propenylgroup (an allyl group) and a butynyl group. Examples of branched alkenylgroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

The chain alkyl group or chain alkenyl group for Ra′⁴ to Ra′⁶ may have asubstituent. Examples of the substituent for the chain alkyl group orchain alkenyl group represented by Ra′⁴ to Ra′⁶ include a hydroxy groupand an ether bond (—O—).

The cyclic hydrocarbon group for Ra′⁴ to Ra′⁶ may be a polycyclic groupor a monocyclic group. Further, the cyclic hydrocarbon group for Ra′⁴ toRa′⁶ may be an alicyclic hydrocarbon group or a fused cyclic group inwhich an aromatic ring is fused with an alicyclic hydrocarbon group.

As the monocyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a monocycloalkane or amonocycloalkene is preferable. The monocycloalkane preferably has 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. The monocycloalkene preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentene and cyclohexene.

As the polycyclic aliphatic hydrocarbon group, a group in which 1hydrogen atom has been removed from a polycycloalkane or apolycycloalkene is preferable. The polycycloalkane preferably has 7 to12 carbon atoms, and examples thereof include adamantane, norbomane,isobomane, tricyclodecane and tetracyclododecane. The polycycloalkenepreferably has 7 to 12 carbon atoms, and examples thereof includeadamantene, norbomene, isobomene, tricyclodecene and tetracyclododecene.

Examples of the fused cyclic group in which an aromatic ring is fusedwith an alicyclic hydrocarbon group include a group in which onehydrogen atom has been removed from an aliphatic ring of a bicycliccompound, such as tetrahydronaphthalene or indane.

The cyclic aliphatic hydrocarbon group for Ra′⁴ to Ra′⁶ may have part ofthe carbon atoms constituting the ring structure thereof substitutedwith a substituent containing a hetero atom. As the substituentcontaining a hetero atom, —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O—is preferable.

The aromatic hydrocarbon group for Ra′⁴ to Ra′⁶ is a hydrocarbon grouphaving an aromatic ring. The aromatic hydrocarbon group preferably has 3to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 10 carbon atoms. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup represented by R¹⁰¹ include benzene, fluorene, naphthalene,anthracene, phenanthrene and biphenyl; and aromatic hetero rings inwhich part of the carbon atoms constituting the aforementioned aromaticrings has been substituted with a hetero atom. Examples of the heteroatom within the aromatic hetero rings include an oxygen atom, a sulfuratom and a nitrogen atom. Specific examples of the aromatic hetero ringinclude a thiophene ring, a furan ring and a pyridine ring.

Specific examples of the aromatic hydrocarbon group represented by R¹⁰¹include a group in which one hydrogen atom has been removed from theaforementioned aromatic ring (i.e., an aryl group, such as a phenylgroup or a naphthyl group), and a group in which one hydrogen of theaforementioned aromatic ring has been substituted with an alkylene group(e.g., an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

The cyclic hydrocarbon group for Ra′⁴ to Ra′⁶ may have a substituent.Examples of the substituent for the cyclic hydrocarbon group representedby Ra′⁴ to Ra′⁶ include a halogen atom (a fluorine atom, a chlorineatom, a bromine atom or an iodine atom), —R^(P1), —R^(P2)—O—R^(P1),—R^(P2)—CO—R^(P1), —R^(P2)—CO—OR^(P1), —R^(P2)—O—CO—R^(P1), —R^(P2)—OH,—R^(P2)—CN or —R^(P2)—COOH (hereafter, these substituents are sometimescollectively referred to as “Ra⁰⁶”).

Here, R^(P1) is a monovalent chain saturated hydrocarbon group having 1to 10 carbon atoms, a monovalent aliphatic cyclic saturated hydrocarbongroup having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbongroup having 6 to 30 carbon atoms. Further, RP² is a single bond, adivalent chain saturated hydrocarbon group having 1 to 10 carbon atoms,a divalent aliphatic cyclic saturated hydrocarbon group having 3 to 20carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30carbon atoms.

Here, a portion or all of the hydrogen atoms having the chain saturatedhydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, andthe aromatic hydrocarbon group for RP¹ and RP² may be substituted with afluorine atom. The aliphatic cyclic hydrocarbon group may have 1 or moresubstituents of 1 kind, or 1 or more substituents of a plurality ofkinds.

Examples of the monovalent chain saturated hydrocarbon group having 1 to10 carbon atoms include a methyl group, an ethyl group, a propyl group,a butyl group, a pentyl group, a hexyl group, a heptyl group, an octylgroup, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon grouphaving 3 to 20 carbon atoms include a monocyclic aliphatic saturatedhydrocarbon group such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecyl group, and a cyclododecyl group; and a polycyclicaliphatic saturated hydrocarbon group such as a bicyclo[2.2.2]octanylgroup, a tricyclo[5.2.1.02,6]decanyl group, atricyclo[3.3.1.13,7]decanyl group, atetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 30carbon atoms include a group obtained by removing one hydrogen atom fromthe aromatic hydrocarbon ring such as benzene, biphenyl, fluorene,naphthalene, anthracene, and phenanthrene.

In formula (a1-r-2), in the case where Ra′⁵ and Ra′⁶ are mutually bondedto form a ring, a group represented by general formula (a1-r2-1) shownbelow, a group represented by general formula (a1-r2-2) shown below, anda group represented by general formula (a1-r2-3) shown below may begiven as preferable examples.

On the other hand, in formula (a1-r-2), in the case where Ra′⁴ to Ra′⁶are not mutually bonded and independently represent a hydrocarbon group,the group represented by general formula (a1-r2-4) shown below may begiven as a preferable example.

In formula (a1-r2-1), Ra′¹⁰ represents an alkyl group having 1 to 10carbon atoms; Ra′¹¹ is a group which forms an aliphatic cyclic grouptogether with a carbon atom having Ra′¹⁰ bonded thereto, or a fusedcyclic group in which an aromatic ring is fused with an alicyclic group,together with a carbon atom having Ra′¹⁰ bonded thereto. In formula(a1-r2-2), Ya represents a carbon atom; Xa represents a group whichforms a cyclic hydrocarbon group together with Ya, provided that part orall of the hydrogen atoms of the cyclic hydrocarbon group may besubstituted; Ra⁰¹ to Ra⁰³ each independently represents a hydrogen atom,a monovalent saturated chain hydrocarbon group of 1 to 10 carbon atomsor a monovalent saturated aliphatic cyclic hydrocarbon group of 3 to 20carbon atoms, provided that part or all of the hydrogen atoms of thesaturated chain hydrocarbon or the saturated aliphatic cyclichydrocarbon may be substituted; two or more of Ra⁰¹ to Ra⁰³ may bemutually bonded to form a cyclic structure. and * represents a valencebond. In formula (a1-r2-3), Yaa represents a carbon atom; Xaa representsa group which forms an aliphatic cyclic group together with Yaa; Ra⁰⁴represents an aromatic hydrocarbon group which may have a substituent.

* represents a bonding site. In formula (a1-r2-4), Ra′¹² and Ra′¹³ eachindependently represent a monovalent chain saturated hydrocarbon grouphaving 1 to 10 carbon atoms or a hydrogen atom, provided that part orall of the hydrogen atoms of the saturated hydrocarbon group may besubstituted; Ra′¹⁴ represents an aromatic hydrocarbon group which mayhave a substituent; and * represents a bonding site (the same definitionhereafter).

In the formula (a1-r2-1), as the alkyl group of 1 to 10 carbon atoms forRa′¹⁰ the same groups as described above for the linear or branchedalkyl group for Ra′³ in the formula (a1-r-1) are preferable.

Ra′¹⁰ is preferably an alkyl group of 1 to 5 carbon atoms.

In formula (a1-r2-1), as the alicyclic group formed by Ra′¹¹ togetherwith a carbon atom having Ra′¹⁰ bonded thereto, or the fused cyclicgroup in which an aromatic ring is fused with an alicyclic hydrocarbongroup formed by Ra′¹¹ together with a carbon atom having Ra′¹⁰ bondedthereto, a cyclic group described above for Ra′⁴ to Ra′⁶ in theaforementioned formula (a1-r-2) is preferable, a group in which onehydrogen atom has been removed form a monocycloalkane or apolycycloalkane is more preferable, a group in which one hydrogen atomhas been removed from cyclopentane, cyclohexane, adamantane, norbomane,isobomane, tricyclodecane or tetracyclododecane is still morepreferable, and a group in which one hydrogen atom has been removed fromcyclopentane or adamantane is most preferable.

The alicyclic group formed by Ra′¹¹ together with a carbon atom havingRa′¹⁰ bonded thereto may have part of the carbon atoms constituting thering structure thereof substituted with a substituent containing ahetero atom. As the substituent containing a hetero atom, —O—,—C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O— is preferable.

In formula (a1-r2-2), as the cyclic hydrocarbon group formed by Xatogether with Ya, a cyclic hydrocarbon group described above for Ra′⁴ toRa′⁶ in the aforementioned formula (a1-r-2) is preferable, a group inwhich one hydrogen atom has been removed from a monocycloalkane is morepreferable, a group in which one hydrogen atom has been removed fromcyclopentane or cyclohexane is still more preferable, and a group inwhich one hydrogen atom has been removed from cyclopentane is still morepreferable.

The cyclic hydrocarbon group which Xa forms with Ya may have asubstituent. The substituent is the same as defined for the substituentfor the cyclic hydrocarbon group represented by Ra′⁴ to Ra′⁶ in theaforementioned formula (a1-r-2).

In formula (a1-r2-2), examples of the monovalent saturated chainhydrocarbon group of 1 to 10 carbon atoms for Ra⁰¹ to Ra⁰³ include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon grouphaving 3 to 20 carbon atoms for Ra⁰¹ to Ra⁰³ include a monocyclicaliphatic saturated hydrocarbon group such as a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptylgroup, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group;and a polycyclic aliphatic saturated hydrocarbon group such as abicyclo[2.2.2] octanyl group, a tricyclo[5.2.1.02,6] decanyl group, atricyclo[3.3.1.13,7]decanyl group, atetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.

Among these examples, in terms of ease in synthesis of the monomericcompound for deriving the structural unit (a0), Ra⁰¹ to Ra⁰³ ispreferably a hydrogen atom or a monovalent saturated hydrocarbon grouphaving 1 to 10 carbon atoms, more preferably a hydrogen atom, a methylgroup or an ethyl group, and most preferably a hydrogen atom.

As the substituent for the saturated chain hydrocarbon group orsaturated cyclic aliphatic hydrocarbon group represented by Ra⁰¹ toRa⁰³, for example, the same substituents as those described above forRa⁰⁵ may be mentioned.

Examples of the group containing a carbon-carbon double bond which isgenerated by forming a cyclic structure in which two or more of Ra⁰¹ toRa⁰³ are bonded to each other include a cyclopentenyl group, acyclohexenyl group, a methyl cyclopentenyl group, a methyl cyclohexenylgroup, a cyclopentylideneethenyl group, and a cyclohexylidenethenylgroup. Among these examples, from the viewpoint of the ease of synthesisof the monomer compound which derives the structural unit (a1), acyclopentenyl group, a cyclohexenyl group, and a cyclopentylidenethenylgroup are preferable.

In formula (a1-r2-3), as the alicyclic group formed by Xaa together withYaa, a cyclic hydrocarbon group described above for Ra′⁴ to Ra′⁶ in theaforementioned formula (a1-r-2) is preferable, a group in which onehydrogen atom has been removed from a monocycloalkane is morepreferable, and a group in which one hydrogen atom has been removed fromcyclopentane or cyclohexane is still more preferable.

In general formula (a1-r2-3), examples of the aromatic hydrocarbon groupfor Ra⁰⁴ include a group obtained by removing one or more hydrogen atomsfrom an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Amongthese examples, as Ra⁰⁴, a group in which one or more hydrogen atomshave been removed from an aromatic hydrocarbon group having 6 to 15carbon atoms is preferable, a group in which one or more hydrogen atomshave been removed from benzene, naphthalene, anthracene, phenanthrene,thiophene or furan is more preferable, a group in which one or morehydrogen atoms have been removed from benzene, naphthalene or anthraceneis still more preferable, and a group in which one or more hydrogenatoms have been removed from benzene is most preferable.

Examples of the substituent that Ra⁰⁴ in general formula (a1-r2-3) mayhave include a methyl group, an ethyl group, a propyl group, a hydroxylgroup, a carboxyl group, a halogen atom (a fluorine atom, a chlorineatom, a bromine atom, or the like), an alkoxy group (a methoxy group, anethoxy group, a propoxy group, a butoxy group, or the like), and analkyloxycarbonyl group.

In general formula (a1-r2-4), Ra′¹² and Ra′¹³ each independentlyrepresent a monovalent chain saturated hydrocarbon group having 1 to 10carbon atoms or a hydrogen atom. With respect to Ra′¹² and Ra′¹³,examples of the monovalent chain saturated hydrocarbon group having 1 to10 carbon atoms include the same monovalent chain saturated hydrocarbongroup having 1 to 10 carbon atoms as that for Ra⁰¹ to Ra⁰³ provided thatpart or all of the hydrogen atoms of the saturated hydrocarbon group maybe substituted;

Among these examples, as Ra′¹² and Ra′¹³, a hydrogen atom and an alkylgroup having 1 to 5 carbon atoms are preferable, an alkyl group having 1to 5 carbon atoms is further preferable, a methyl group and an ethylgroup are still further preferable, and a methyl group is particularlypreferable.

In the case where the chain saturated hydrocarbon group represented byRa′¹² and Ra′¹³ is substituted, examples of the substituent include thesame group as that of Ra⁰⁵.

In general formula (a1-r2-4), Ra′¹⁴ is an aromatic hydrocarbon groupwhich may have a substituent. Examples of the hydrocarbon group forRa′¹⁴ include the same aromatic hydrocarbon groups as those exemplifiedin the description for Ra⁰⁴. Among these examples, Ra′¹⁴ is preferably agroup obtained by removing one or more hydrogen atoms from the aromatichydrocarbon group having 6 to 15 carbon atoms, is further preferably agroup obtained by removing one or more hydrogen atoms from benzene,naphthalene, anthracene, or phenanthrene, is still further preferably agroup obtained by removing one or more hydrogen atoms from benzene,naphthalene, or anthracene, is particularly preferably a group obtainedby removing one or more hydrogen atoms from naphthalene or anthracene,and is most preferably a group obtained by removing one or more hydrogenatoms from naphthalene.

Examples of the substituent that Ra′¹⁴ may have include the same groupas the substituent that Ra⁰⁴ may have.

In the case where Ra′¹⁴ in general formula (a1-r2-4) is a naphthylgroup, a position which is bonded to a tertiary carbon atom in generalformula (a1-r2-4) may be 1-position and 2-position of the naphthylgroup.

In the case where Ra′¹⁴ in general formula (a1-r2-4) is an anthrylgroup, a position which is bonded to a tertiary carbon atom in generalformula (a1-r2-4) may be any one of 1-position, 2-position, and9-position of the anthryl group.

Specific examples of the group represented by the aforementioned formula(a1-r2-1) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-2) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-3) are shown below.

Specific examples of the group represented by the aforementioned formula(a1-r2-4) are shown below.

Tertiary Alkyloxycarbonyl Acid Dissociable Group

Examples of the acid dissociable group for protecting a hydroxy group asa polar group include the acid dissociable group represented by generalformula (a1-r-3) shown below (hereafter, for convenience, referred to as“tertiary alkyloxycarbonyl-type acid dissociable group”).

In the formula, Ra′⁷ to Ra′⁹ each independently represents an alkylgroup.

In the formula (a1-r-3), Ra′⁷ to Ra′⁹ is preferably an alkyl group of 1to 5 carbon atoms, and more preferably an alkyl group of 1 to 3 carbonatoms.

Further, the total number of carbon atoms within the alkyl group ispreferably 3 to 7, more preferably 3 to 5, and most preferably 3 or 4.

In formula (a0), as the acid dissociable group for Ra⁰⁰, a grouprepresented by any one of the aforementioned formula (a1-r2-1) to(a1-r2-4) is preferable, and a group represented by the aforementionedformula (a1-r2-1) or (a1-r2-3) is more preferable.

Specific examples of the structural unit (a0) are shown below. In theformulae, R⁰ is the same as defined above.

As the structural unit (a0) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

In the component (A1), the amount of the structural unit (a0) based onthe combined total (100 mol %) of all structural units constituting thecomponent (A1) is preferably 30 to 75 mol %, more preferably 35 to 70mol %, and still more preferably 40 to 65 mol %.

When the amount of the structural unit (a0) is at least as large as thelower limit of the above-mentioned range, various lithography propertiessuch as sensitivity, resolution and roughness may be improved. On theother hand, when the amount of the structural unit (a0) is no more thanthe upper limit of the above-mentioned range, a good balance may beachieved with the other structural units.

Other Structural Units:

If desired, the component (A1) may include, in addition to thestructural unit (a0), other structural unit.

Examples of the other structural units include a structural unit (a10)represented by general formula (a10-1); a structural unit (a1)containing an acid decomposable group which exhibits increased polarityby the action of acid (provided that structural units which fall underthe definition of the structural unit (a0) is excluded); a structuralunit (a2) containing a lactone-containing cyclic group, an —SO₂—containing cyclic group or a carbonate-containing cyclic group; astructural unit (a3) containing a polar group-containing aliphatichydrocarbon group (provided that the structural units that fall underthe definition of structural units (a1) and (a2) are excluded); astructural unit (a4) containing an acid non-dissociable aliphatic cyclicgroup; and a structural unit derived from styrene or a derivativethereof.

Structural Unit (a10):

The structural unit (a10) is a structural unit represented by generalformula (a10-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;Ya^(x1) represents a single bond or a divalent linking group; Wa^(x1)represents an aromatic hydrocarbon group having a valency of(n_(ax1)+1); and n_(ax1) represents an integer of 1 or more.

In general formula (a10-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group having 1 to 5 carbon atoms for R, a linear orbranched alkyl group of 1 to 5 carbon atoms is preferable, and specificexamples thereof include a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

The halogenated alkyl group of 1 to 5 carbon atoms represented by R is agroup in which part or all of the hydrogen atoms of the aforementionedalkyl group of 1 to 5 carbon atoms have been substituted with halogenatoms. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and inview of industrial availability, a hydrogen atom, a methyl group or atrifluoromethyl group is more preferable, a hydrogen atom or a methylgroup is still more preferable, and a hydrogen atom is most preferable.

In formula (a10-1), Ya^(x1) represents a single bond or a divalentlinking group.

In formula (a10-1), the divalent linking group for Ya^(x1) is the sameas defined for the divalent linking group for Va^(x1) in theaforementioned formula (a0).

Among the above examples, as Ya^(x1), a single bond, an ester bond[—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of these is preferable, and a singlebond or an ester bond [—C(═O)—O—, —O—C(═O)—] is more preferable.

In formula (a10-1), Wa^(x1) represents an aromatic hydrocarbon grouphaving a valency of (n_(ax1)+1).

Examples of the aromatic hydrocarbon group for Wa^(x1) include a groupobtained by removing (n_(ax1)+1)hydrogen atoms from an aromatic ring.The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having (4n+2)π electrons, and may be eithermonocyclic or polycyclic. The aromatic ring preferably has 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, and still morepreferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbonatoms. Specific examples of the aromatic ring include an aromatichydrocarbon ring, such as benzene, naphthalene, anthracene orphenanthrene; and an aromatic heterocyclic ring in which part of thecarbon atoms constituting the aromatic hydrocarbon ring has beensubstituted with a heteroatom. Examples of the hetero atom within thearomatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom. Specific examples of the aromatic hetero ring include apyridine ring and a thiophene ring.

Further examples of the aromatic hydrocarbon group for Wa^(x1) include agroup in which (n_(ax1)+1) hydrogen atom(s) has been removed from anaromatic group containing 2 or more aromatic rings (e.g., biphenyl,fluorene, or the like).

Among the above examples, as Wa^(x1), a group in which (n_(ax1)+1)hydrogen atoms have been removed from benzene, naphthalene, anthraceneor biphenyl is preferable, a group in which (n_(ax1)+1) hydrogen atomshave been removed from benzene or naphthalene is more preferable, and agroup in which (n_(ax1)+1) hydrogen atoms have been removed from benzeneis still more preferable.

In formula (a10-1), n_(ax1) is an integer of 1 or more, preferably aninteger of 1 to 10, more preferably an integer of 1 to 5, still morepreferably 1, 2 or 3, and most preferably 1 or 2.

Specific examples of the structural unit (a10) represented by formula(a10-1) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a10) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) includes the structural unit (a10), the amountof the structural unit (a10) based on the combined total of allstructural units constituting the component (A1) (100 mol %) ispreferably 15 to 70 mol %, more preferably 20 to 60 mol %, and stillmore preferably 25 to 55 mol %.

When the amount of the structural unit (a10) is at least as large as thelower limit of the above preferable range, the sensitivity may be morereliably enhanced. On the other hand, when the amount of the structuralunit (a0) is no more than the upper limit of the above-mentioned range,a good balance may be reliably achieved with the other structural units.

Structural Unit (a1):

The structural unit (a1) is a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid (provided that structural units which fall under the definition ofthe structural unit (a0) is excluded).

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) may be given.

The “acid dissociable group” refers to both (i) a group in which thebond between the acid dissociable group and the adjacent atom is cleavedby the action of acid; and (ii) a group in which one of the bonds iscleaved by the action of acid, and then a decarboxylation reactionoccurs, thereby cleaving the bond between the acid dissociable group andthe adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes, and the solubility in an alkali developingsolution is relatively increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

Examples of the acid dissociable group include groups which have beenproposed as acid dissociable groups for the base resin of a conventionalchemically amplified resist composition.

Specific examples of acid dissociable groups for the base resin of aconventional chemically amplified resist composition include“acetal-type acid dissociable group”, “tertiary alkyl ester-type aciddissociable group” and “tertiary alkyloxycarbonyl acid dissociablegroup” described above in relation to the acid dissociable group for R⁰⁰in the aforementioned formula (a0).

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent; astructural unit derived from an acrylamide; a structural unit derivedfrom hydroxystyrene or a hydroxystyrene derivative in which at least apart of the hydrogen atom of the hydroxy group is protected with asubstituent containing an acid decomposable group; and a structural unitderived from vinylbenzoic acid or a vinylbenzoic acid derivative inwhich at least a part of the hydrogen atom within —C(═O)—OH is protectedwith a substituent containing an acid decomposable group.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of preferable structural units for the structural unit(a1) include structural units represented by general formula (a1-1) or(a1-2) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va¹represents a divalent hydrocarbon group optionally having an ether bond;n_(a1) represents an integer of 0 to 2; Ra¹ represents an aciddissociable group represented by the aforementioned formula (a1-r-1) or(a1-r-2); Wa¹ represents a hydrocarbon group having a valency ofn_(a2)+1; n_(a2) represents an integer of 1 to 3; and Ra² represents anacid dissociable group represented by the aforementioned formula(a1-r-1) or (a1-r-3).

In formula (a1-1), R and Va¹ are the same as defined for R and Va¹ inthe aforementioned formula (a0-1-1), respectively.

In formula (a1-1), Ra¹ represents an acid dissociable group representedby the aforementioned formula (a1-r-1) or (a1-r-2).

In the aforementioned formula (a1-2), the hydrocarbon group for Wa¹having a valency of n_(a2)+1 may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic cyclic grouprefers to a hydrocarbon group that has no aromaticity, and may be eithersaturated or unsaturated, but is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring inthe structure thereof, and a combination of the linear or branchedaliphatic hydrocarbon group and the aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

Specific examples of structural unit represented by formula (a1-1) areshown below. In the formulae shown below, R^(α) represents a hydrogenatom, a methyl group or a trifluoromethyl group.

Specific examples of structural unit represented by formula (a1-2) areshown below.

As the structural unit (a1) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

From the viewpoint that the properties of the lithography (sensitivity,shape, and the like) by electron beam and EUV are more likely to beenhanced, the structural unit (a1) is further preferably a structuralunit represented by general formula (a1-1).

Further, in terms of reducing roughness, the acid dissociable group forRa¹ in the aforementioned formula (a1-1) is preferably an aciddissociable group represented by general formula (a1-r2-11) or(a1-r2-21) shown below.

In formula (a1-r2-11), Ra′¹⁰ represents an alkyl group of 1 to 10 carbonatoms; Ra′¹¹¹ is a group which forms a monocyclic alicyclic grouptogether with a carbon atom having Ra′¹⁰ bonded thereto. In formula(a1-r2-2), Ya represents a carbon atom; Xb represents a group whichforms a monocyclic alicyclic hydrocarbon group together with Yb,provided that part or all of the hydrogen atoms of the monocyclicalicyclic hydrocarbon group may be substituted; Ra⁰¹ to Ra⁰³ eachindependently represents a hydrogen atom, a monovalent saturated chainhydrocarbon group of 1 to 10 carbon atoms or a monovalent saturatedaliphatic cyclic hydrocarbon group of 3 to 20 carbon atoms, providedthat part or all of the hydrogen atoms of the saturated chainhydrocarbon or the saturated aliphatic cyclic hydrocarbon may besubstituted; two or more of Ra⁰¹ to Ra⁰³ may be mutually bonded to forma cyclic structure. and * represents a valence bond.

In formula (a1-r2-11), Ra′¹⁰ is the same as defined for Ra′¹⁰ in theaforementioned formula (a1-r2-1).

In formula (a1-r2-11), as the monocyclic alicyclic hydrocarbon which isformed by Ra′¹¹¹ together with the carbon atom bonded to Ra′¹⁰, the samegroups as those described above for the monocyclic aliphatic hydrocarbongroup for Ra′³ in formula (a1-r-1) are preferable.

In formula (a1-r2-21), as the monocyclic aliphatic hydrocarbon groupformed by Xb together with Ya, a group in which 1 or more hydrogen atomshave been removed from the monovalent monocyclic hydrocarbon group forRa′³ in the aforementioned formula (a1-r-1) may be mentioned.

The monocyclic aliphatic hydrocarbon group formed by Xb together with Yamay have a substituent. Examples of substituents include the samesubstituents as those which the cyclic hydrocarbon group for Ra′³ mayhave. Among these examples, as the monocyclic aliphatic hydrocarbongroup formed by Xb together with Ya, a group in which one hydrogen atomhas been removed from a monocycloalkane is preferable, and a group inwhich one hydrogen atom has been removed from cyclopentane orcyclohexane is more preferable.

In formula (a1-r2-21), Ra⁰¹ to Ra⁰³ are the same as defined for Ra⁰¹ toRa⁰³ in the aforementioned formula (a1-r2-2), respectively.

In the component (A1), the amount of the structural unit (a1) based onthe combined total (100 mol %) of all structural units constituting thecomponent (A1) is preferably 5 to 70 mol %, more preferably 5 to 65 mol%, and still more preferably 5 to 50 mol %.

When the amount of the structural unit (a1) is at least as large as thelower limit of the above-mentioned range, a resist pattern may bereliably obtained, and various lithography properties such assensitivity, resolution and roughness are further improved. On the otherhand, when the amount of the structural unit (a1) is no more than theupper limit of the above-mentioned range, a good balance may be achievedwith the other structural units.

Structural Unit (a2):

The component (A1) may include, in addition to the structural unit (a0),a structural unit (a2) containing a lactone-containing cyclic group, an—SO₂— containing cyclic group or a carbonate-containing cyclic group.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group, the —SO₂— containing cyclic group orthe carbonate-containing cyclic group within the structural unit (a2) iseffective in improving the adhesion between the resist film and thesubstrate. In addition, by virtue of containing the structural unit(a2), for example, the acid diffusion length is appropriately adjusted,the adhesion of the resist film to the substrate is enhanced, or thesolubility during development is appropriately adjusted. As a result,the lithography properties are enhanced.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the structural unit (a2) is notparticularly limited, and an arbitrary structural unit may be used.Specific examples include groups represented by general formulae(a2-r-1) to (a2-r-7) shown below.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂— containing cyclic group; A″ represents an oxygen atom, a sulfuratom, or an alkylene group of 1 to 5 carbon atoms which may contain anoxygen atom or a sulfur atom; n′ represents an integer of 0 to 2; and m′represents 0 or 1.

In formulae (a2-r-1) to (a2-r-7), the alkyl group for Ra′²¹ ispreferably an alkyl group of 1 to 6 carbon atoms. The alkyl group ispreferably a linear alkyl group or a branched alkyl group. Specificexamples include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a neopentyl group and a hexylgroup. Among these, a methyl group or ethyl group is preferable, and amethyl group is most preferable.

The alkoxy group for Ra′²¹ is preferably an alkoxy group of 1 to 6carbon atoms.

The alkoxy group is preferably a linear or branched alkoxy group.Specific examples of the alkoxy groups include the aforementioned alkylgroups for Ra′²¹ having an oxygen atom (—O—) bonded thereto.

As examples of the halogen atom for Ra′²¹, a fluorine atom, chlorineatom, bromine atom and iodine atom may be given. Among these, a fluorineatom is preferable.

Examples of the halogenated alkyl group for Ra′²¹ include groups inwhich part or all of the hydrogen atoms within the aforementioned alkylgroup for Ra′²¹ has been substituted with the aforementioned halogenatoms. As the halogenated alkyl group, a fluorinated alkyl group ispreferable, and a perfluoroalkyl group is particularly desirable.

With respect to —COOR″ and —OC(═O)R″ for Ra′²¹, R″ represents a hydrogenatom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂— containing cyclic group.

The alkyl group for R″ may be linear, branched or cyclic, and preferablyhas 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and still morepreferably 5 to 10 carbon atoms. Specific examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane or cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobomane,tricyclodecane or tetracyclododecane.

Examples of the lactone-containing cyclic group for R″ include groupsrepresented by the aforementioned general formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group for R″ is the same as defined forthe carbonate-containing cyclic group described later. Specific examplesof the carbonate-containing cyclic group include groups represented bygeneral formulae (ax3-r-1) to (ax3-r-3).

The —SO₂— containing cyclic group for R″ is the same as defined for the—SO₂-containing cyclic group described later. Specific examples of the—SO₂— containing cyclic group include groups represented by generalformulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group for Ra′²¹ preferably has 1 to 6 carbon atoms, andspecific examples thereof include the alkyl groups for Ra′²¹ in which atleast one hydrogen atom has been substituted with a hydroxy group.

In formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene group of 1to 5 carbon atoms represented by A″, a linear or branched alkylene groupis preferable, and examples thereof include a methylene group, anethylene group, an n-propylene group and an isopropylene group. Examplesof alkylene groups that contain an oxygen atom or a sulfur atom includethe aforementioned alkylene groups in which —O— or —S— is bonded to theterminal of the alkylene group or present between the carbon atoms ofthe alkylene group. Specific examples of such alkylene groups include—O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—. As A″, an alkylene groupof 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylenegroup of 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7) are shown below.

An “—SO₂— containing cyclic group” refers to a cyclic group having aring containing —SO₂— within the ring structure thereof, i.e., a cyclicgroup in which the sulfur atom (S) within —SO₂— forms part of the ringskeleton of the cyclic group. The ring containing —SO₂— within the ringskeleton thereof is counted as the first ring. A cyclic group in whichthe only ring structure is the ring that contains —SO₂— in the ringskeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulas (a5-r-1) to (a5-r-4) shown below.

In the formulae, each Ra′⁵¹ independently represents an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, —COOR″,—OC(═O)R″, a hydroxyalkyl group or a cyano group; R″ represents ahydrogen atom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂-containing cyclic group; A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms with or without an oxygen atom or a sulfur atom;

and n′ represents an integer of 0 to 2.

In general formulae (a5-r-1) and (a5-r-2), A″ is the same as defined forA″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′⁵¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (a5-r-1) to (a5-r-4) are shown below. In the formulaeshown below, “Ac” represents an acetyl group.

The term “carbonate-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)—O— structure (carbonate ring).The term “carbonate ring” refers to a single ring containing a—O—C(═O)—O— structure, and this ring is counted as the first ring. Acarbonate-containing cyclic group in which the only ring structure isthe carbonate ring is referred to as a monocyclic group, and groupscontaining other ring structures are described as polycyclic groupsregardless of the structure of the other rings. The carbonate-containingcyclic group may be either a monocyclic group or a polycyclic group.

The carbonate-containing cyclic group is not particularly limited, andan arbitrary group may be used. Specific examples include groupsrepresented by general formulae (ax3-r-1) to (ax3-r-3) shown below.

In the formulae, each Ra′^(x31) independently represents an alkyl group,an alkoxy group, a halogen atom, a halogenated alkyl group, —COOR″,—OC(═O)R″, a hydroxyalkyl group or a cyano group; R″ represents ahydrogen atom, an alkyl group, a lactone-containing cyclic group, acarbonate-containing cyclic group or an —SO₂-containing cyclic group; A″represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5carbon atoms with or without an oxygen atom or a sulfur atom; p′represents an integer of 0 to 3; and q′ is 0 or 1.

In general formulae (ax3-r-2) and (ax3-r-3), A″ is the same as definedfor A″ in general formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′³¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (ax3-r-1) to (ax3-r-3) are shown below.

As the structural unit (a2), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

Specific examples of preferable structural units for the structural unit(a2) include structural units represented by general formula (a2-1)shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ya²¹represents a single bond or a divalent linking group; La²¹ represents—O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—; and R′ represents ahydrogen atom or a methyl group; provided that, when La²¹ represents—O—, Ya²¹ does not represent —CO—; and Ra²¹ represents alactone-containing cyclic group, an —SO₂— containing cyclic group or acarbonate-containing cyclic group.

In the formula (a2-1), R is the same as defined above.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In the formula (a2-1), the divalent linking group for Ya²¹ is notparticularly limited, and preferable examples thereof include a divalenthydrocarbon group which may have a substituent and a divalent linkinggroup containing a hetero atom.

The divalent hydrocarbon group for Ya²¹ is the same as defined for thedivalent hydrocarbon group represented by Va¹ in the aforementionedformula (a1-1). Examples of the substituent for the divalent hydrocarbongroup represented by Ya²¹ include an alkyl group of 1 to 5 carbon atoms,an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxygroup, a carbonyl group.

In the case where Ya²¹ represents a divalent linking group containing ahetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═NH)— (may besubstituted with a substituent such as an alkyl group, an acyl group orthe like), —S—, —S(═O)₂—, —S(═O)₂—O—, and a group represented by generalformula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [inthe formulae, Y²¹ and Y²² each independently represents a divalenthydrocarbon group which may have a substituent, O represents an oxygenatom, and m′ represents an integer of 0 to 3].

In the case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group or the like.The substituent (an alkyl group, an acyl group or the like) preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 5.

In general formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represents a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe aforementioned divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]m″—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]m″—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

Ya²¹ preferably represents an ester bond [—C(═O)—O—], an ether bond(—O—), a linear or branched alkylene group, a combination of these, or asingle bond.

In formula (a2-1), La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—,—CONHCO— or —CONHCS—.

R′ represents a hydrogen atom or a methyl group.

However, when La²¹ represents —O—, Ya²¹ does not represent —CO—.

In the formula (a2-1), Ra²¹ represents a lactone-containing cyclicgroup, an —SO₂— containing cyclic group or a carbonate-containing cyclicgroup.

Preferable examples of the lactone-containing cyclic group, the—SO₂-containing cyclic group and the carbonate-containing cyclic groupfor Ra²¹ include groups represented by general formulae (a2-r-1) to(a2-r-7), groups represented by general formulae (a5-r-1) to (a5-r-4)and groups represented by general formulae (ax3-r-1) to (ax3-r-3).

Among the above examples, as Ra²¹, a lactone-containing cyclic group oran —SO₂— containing cyclic group is preferable, and a group representedby the aforementioned general formula (a2-r-1), (a2-r-2), (a2-r-6) or(a5-r-1) is more preferable. Specifically, a group represented by any ofchemical formulae (r-1c-1-1) to (r-1c-1-7), (r-1c-2-1) to (r-1c-2-18),(r-1c-6-1), (r-s1-1-1) and (r-s1-1-18) is still more preferable.

As the structural unit (a2) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds may be used.

When the component (A1) contains the structural unit (a2), the amount ofthe structural unit (a2) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 80mol %, more preferably 3 to 70 mol %, still more preferably 5 to 60 mol%, and most preferably 5 to 50 mol %.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above preferable range, the effect of using thestructural unit (a2) may be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above preferable range, a good balance may be achieved withthe other structural units, and various lithography properties may beimproved.

Structural Unit (a3):

The component (A1) may include, in addition to the structural unit (a0),a structural unit (a3) containing a polar group-containing aliphatichydrocarbon group (provided that the structural units that fall underthe definition of structural units (a1) and (a2) are excluded).

By virtue of the component (A1) including the structural unit (a3),various advantages may be obtained, such as appropriate adjustment ofacid diffusion length, enhancement of adhesion of a resist film to asubstrate, appropriate adjustment of solubility of the resist duringdeveloping, and improvement in etching resistance, which may lead toimprovement in lithography properties.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups may be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbomane, isobomane, tricyclodecane or tetracyclododecane.Of these polycyclic groups, groups in which two or more hydrogen atomshave been removed from adamantane, norbomane or tetracyclododecane arepreferred industrially.

As the structural unit (a3), there is no particular limitation as longas it is a structural unit containing a polar group-containing aliphatichydrocarbon group, and an arbitrary structural unit may be used.

The structural unit (a3) is preferably a structural unit derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains apolar group-containing aliphatic hydrocarbon group.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) contains the structural unit (a3), the amount ofthe structural unit (a3) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 50mol %, more preferably 3 to 40 mol %, still more preferably 5 to 30 mol%, and most preferably 10 to 30 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above preferable range, the effect of using thestructural unit (a3) may be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above preferable range, a good balance may be achieved withthe other structural units, and various lithography properties may beimproved.

Structural Unit (a4):

The component (A1) may be further include, in addition to the structuralunit (a0), a structural unit (a4) containing an acid non-dissociable,aliphatic cyclic group.

When the component (A1) includes the structural unit (a4), dry etchingresistance of the resist pattern to be formed is improved. Further, thehydrophobicity of the component (A) is further improved. Increase in thehydrophobicity contributes to improvement in terms of resolution, shapeof the resist pattern and the like, particularly in a solvent developingprocess.

An “acid non-dissociable, aliphatic cyclic group” in the structural unit(a4) refers to a cyclic group which is not dissociated by the action ofthe acid (e.g., acid generated from a structural unit which generatesacid upon exposure or acid generated from the component (B)) uponexposure, and remains in the structural unit.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic cyclic group, and is also derived from anacrylate ester is preferable. As the cyclic group, any of the multitudeof conventional polycyclic groups used within the resin component ofresist compositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) may be used.

As the aliphatic polycyclic group, at least one polycyclic groupselected from amongst a tricyclodecyl group, adamantyl group,tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable in consideration of industrial availability andthe like. These polycyclic groups may be substituted with a linear orbranched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include structural unitsrepresented by general formulae (a4-1) to (a4-7) shown below.

In the formulae, R^(α) is the same as defined above.

As the structural unit (a4) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) contains the structural unit (a4), the amount ofthe structural unit (a4) based on the combined total (100 mol %) of allstructural units constituting the component (A1) is preferably 1 to 40mol %, and more preferably 5 to 20 mol %.

When the amount of the structural unit (a4) is at least as large as thelower limit of the above-mentioned preferable range, the effect of usingthe structural unit (a4) may be satisfactorily achieved. On the otherhand, when the amount of the structural unit (a4) is no more than theupper limit of the above preferable range, a good balance may beachieved with the other structural units, and various lithographyproperties may be improved.

Structural Unit Derived from Styrene or a Derivative Thereof (StructuralUnit (St))

The term “styrene” is a concept including styrene and compounds in whichthe hydrogen atom at the α-position of styrene is substituted with asubstituent such as an alkyl group or a halogenated alkyl group.Examples of the alkyl group as the substituent include an alkyl grouphaving 1 to 5 carbon atoms. Examples of the halogenated alkyl group asthe substituent include a halogenated alkyl group having 1 to 5 carbonatoms. Examples of the “styrene derivative” include styrene which has asubstituent other than a hydroxy group bonded to the benzene ring andmay have the hydrogen atom on the α-position substituted with asubstituent.

Here, the α-position (carbon atom on the α-position) refers to thecarbon atom having the benzene ring bonded thereto, unless specifiedotherwise.

A “structural unit derived from styrene” or “structural unit derivedfrom a styrene derivative” refers to a structural unit that is formed bythe cleavage of the ethylenic double bond of styrene or a styrenederivative.

As the structural unit (st) contained in the component (A1), 1 kind ofstructural unit may be used, or 2 or more kinds of structural units maybe used.

When the component (A1) includes the structural unit (st), the amount ofthe structural unit (st) based on the combined total of all structuralunits constituting the component (A1) (100 mol %) is preferably 1 to 30mol %, and more preferably 3 to 20 mol %.

In the resist composition according to the present embodiment, thecomponent (A1) is preferably a copolymer (component (A1-1)) having astructural unit (a0) and any other desired structural unit.

Specific examples of the component (A1-1) include a polymeric compoundconsisting of a repeating structure of the structural unit (a0) and thestructural unit (a10); a polymeric compound consisting of a repeatingstructure of the structural unit (a0), the structural unit (a10) and thestructural unit (a2); and a polymeric compound consisting of a repeatingstructure of the structural unit (a0), the structural unit (a10) and thestructural unit (a3).

<<Component (A2)>>

In the resist composition of the present embodiment, as the component(A), “a base component which exhibits changed solubility in a developingsolution under action of acid” other than the component (A1) (hereafter,referred to as “component (A2)”) may be used in combination.

As the component (A2), there is no particular limitation, and any of themultitude of conventional base resins used within chemically amplifiedresist compositions may be arbitrarily selected for use.

As the component (A2), one kind of a polymer or a low molecular weightcompound may be used, or a combination of two or more kinds may be used.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography (GPC)) of thecomponent (A1) is not particularly limited, but is preferably 1,000 to50,000, more preferably 2,000 to 30,000, and still more preferably 3,000to 20,000.

When the Mw of the component (A1) is no more than the upper limit of theabove-mentioned preferable range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theMw of the component (A1) is at least as large as the lower limit of theabove-mentioned preferable range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

The dispersity (Mw/Mn) of the component (A1) is not particularlylimited, but is preferably 1.0 to 4.0, more preferably 1.0 to 3.0, andmost preferably 1.0 to 2.5. Here, Mn is the number average molecularweight.

As the component (A), one kind of compound may be used alone, or two ormore kinds of compounds may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, a resist pattern with improvedlithography properties may be reliably formed, such as improvedsensitivity and improved roughness.

In the resist composition of the present embodiment, the amount of thecomponent (A) may be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

Component (B1)

The component (B) is an acid generator component which generates acidupon exposure. In the resist composition of the present embodiment, thecomponent (B) includes at least one member selected from the groupconsisting of a compound (b-1) represented by general formula (b-1)shown below (hereafter, sometimes referred to as “component (b-1)”), acompound (b-2) represented by general formula (b-2) shown below(hereafter, sometimes referred to as “component (b-2)”) and a compound(b-3) represented by general formula (b-3) shown below (hereafter,sometimes referred to as “component (b-3)”) (hereafter, sometimescollectively referred to as “component (B1)”).

In the formulae, R¹⁰¹, R¹⁰⁴ and R¹⁰⁶ each independently represents ahydrocarbon group containing an aromatic ring which may have asubstituent; R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent; R¹⁰²represents a fluorine atom or a fluorinated alkyl group of 1 to 5 carbonatoms; Y¹⁰¹ represents a single bond or a divalent linking groupcontaining an oxygen atom;

V¹⁰¹ to V¹⁰³ each independently represents a single bond, an alkylenegroup or a fluorinated alkylene group; L¹⁰¹ and L¹⁰² each independentlyrepresents a single bond or an oxygen atom; L¹⁰³ to L¹⁰⁵ eachindependently represents a single bond, —CO— or —SO₂—; m represents aninteger of 1 or more; and M′^(m+) represents an m-valent onium cation.

{Anion Moiety}

Anion Moiety of Component (b-1)

In formula (b-1), R¹⁰¹ represents a hydrocarbon group containing anaromatic ring which may have a substituent.

The hydrocarbon group containing an aromatic ring represented by R¹⁰¹preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbonatoms, still more preferably 5 to 20 carbon atoms, and most preferably 6to 18 carbon atoms. Here, the number of carbon atoms within asubstituent(s) is not included in the number of carbon atoms of thearomatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup represented by R¹⁰¹ include benzene, fluorene, naphthalene,anthracene, phenanthrene and biphenyl; and aromatic hetero rings inwhich part of the carbon atoms constituting the aforementioned aromaticrings has been substituted with a hetero atom. Examples of the heteroatom within the aromatic hetero rings include an oxygen atom, a sulfuratom and a nitrogen atom.

Specific examples of the hydrocarbon group containing an aromatic ringrepresented by R¹⁰¹ include a group in which one hydrogen atom has beenremoved from the aforementioned aromatic ring (an aryl group, such as aphenyl group or a naphthyl group), a group in which one hydrogen atom ofthe aforementioned aromatic ring has been substituted with an alkylenegroup (an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group), and a group in which one hydrogenatom has been removed from a condensed ring of the aforementionedaromatic ring and a bridged aliphatic ring such as bicycloheptane orbicyclooctane. The alkylene group (alkyl chain within the arylalkylgroup) preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

In the hydrocarbon group containing an aromatic ring represented byR¹⁰¹, examples of the substituent for the aromatic ring include an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxy group, a carbonyl group and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms, andmore preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, a tert-butyl group, a cyclopentyl group or a cyclohexylgroup.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The carbonyl group as the substituent is a group that substitutes amethylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Among these examples, in the hydrocarbon group containing an aromaticring represented by R¹⁰¹, the substituent for the aromatic ring ispreferably a tert-butyl group, a hydroxy group or a cyclohexyl group.

In formula (b-1), Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

In the case where Y¹⁰¹ is a divalent linking group containing an oxygenatom, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples ofatoms other than an oxygen atom include a carbon atom, a hydrogen atom,a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—), a carbonyl group(—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations of theaforementioned non-hydrocarbon, hetero atom-containing linking groupswith an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto. Examples of divalent linkinggroups containing an oxygen atom include linking groups represented bygeneral formulae (y-a1-1) to (y-a1-9) shown below.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene group of1 to 5 carbon atoms; V′¹⁰² represents a divalent saturated hydrocarbongroup of 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group for V′¹⁰² is preferably analkylene group of 1 to 30 carbon atoms, more preferably an alkylenegroup of 1 to 10 carbon atoms, and still more preferably an alkylenegroup of 1 to 5 carbon atoms.

The alkylene group for V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group for V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group, such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group, suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group, such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group,such as —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylenegroup [—CH₂CH₂CH₂CH₂CH₂—].

Further, part of methylene group within the alkylene group for V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group of 5 to10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group (monocyclic alicyclic hydrocarbon group orpolycyclic alicyclic hydrocarbon group) for R¹⁰¹ in the aforementionedformula (b-1), and a cyclohexylene group, 1,5-adamantylene group or2,6-adamantylene group is preferable.

Y¹⁰¹ is preferably a divalent linking group containing an ether bond ora divalent linking group containing an ester bond, and groupsrepresented by the aforementioned formulas (y-a1-1) to (y-a1-5) arepreferable.

In formula (b-1), V¹⁰¹ represents a single bond, an alkylene group or afluorinated alkylene group. The alkylene group and the fluorinatedalkylene group for V¹⁰¹ preferably has 1 to 4 carbon atoms. Examples ofthe fluorinated alkylene group for V¹⁰¹ include a group in which part orall of the hydrogen atoms within the alkylene group for V¹⁰¹ have beensubstituted with fluorine. Among these examples, as V¹⁰¹, a single bondor a fluorinated alkylene group of 1 to 4 carbon atoms is preferable.

In formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms. R¹⁰² is preferably a fluorine atom or aperfluoroalkyl group of 1 to 5 carbon atoms, and more preferably afluorine atom.

Anion Moiety of Component (b-2)

In formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent. R¹⁰⁴and R¹⁰⁵ may be mutually bonded to form a ring.

Cyclic Group which May have a Substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group. An “aliphatic hydrocarbon group” refersto a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group may be either saturated or unsaturated, but ingeneral, the aliphatic hydrocarbon group is preferably saturated.

The aromatic hydrocarbon group for R¹⁰⁴ and R¹⁰⁵ is a hydrocarbon grouphaving an aromatic ring.

The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, morepreferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbonatoms, still more preferably 6 to 15 carbon atoms, and most preferably 6to 10 carbon atoms. Here, the number of carbon atoms within asubstituent(s) is not included in the number of carbon atoms of thearomatic hydrocarbon group.

In the aromatic hydrocarbon group for R¹⁰⁴ and R¹⁰⁵, specific examplesof the aromatic ring include benzene, biphenyl, fluorene, naphthalene,anthracene, phenanthrene, and an aromatic hetero ring in which part ofthe carbon atoms constituting any of these aromatic rings has beensubstituted with a hetero atom. Examples of the hetero atom within thearomatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom.

Specific examples of the aromatic hydrocarbon group for R¹⁰⁴ and R¹⁰⁵include a group in which one hydrogen atom has been removed from theaforementioned aromatic ring (an aryl group, such as a phenyl group or anaphthyl group), and a group in which one hydrogen atom of theaforementioned aromatic ring has been substituted with an alkylene group(an arylalkyl group, such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

Examples of the cyclic aliphatic hydrocarbon group for R¹⁰⁴ and R¹⁰⁵include aliphatic hydrocarbon groups containing a ring in the structurethereof.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which one hydrogenatom has been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain aliphatic hydrocarbon group, and a group in whichthe alicyclic group is interposed within the aforementioned linear orbranched aliphatic hydrocarbon group, may be given.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which one or more hydrogen atoms have been removed from amonocycloalkane is preferable. The monocycloalkane preferably has 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. As the polycyclic alicyclic hydrocarbon group, a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane is preferable, and the polycyclic group preferably has 7to 30 carbon atoms. Among polycycloalkanes, a polycycloalkane having abridged ring polycyclic skeleton, such as adamantane, norbomane,isobomane, tricyclodecane or tetracyclodpdecane, and a polycycloalkanehaving a condensed ring polycyclic skeleton, such as a cyclic grouphaving a steroid skeleton are preferable.

Among these examples, as the cyclic aliphatic hydrocarbon group for R¹⁰⁴and R¹⁰⁵, a group in which one or more hydrogen atoms have been removedfrom a monocycloalkane or a polycycloalkane is preferable, a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane is more preferable, an adamantyl group or a norbornylgroup is still more preferable, and an adamantyl group is mostpreferable.

The linear or branched aliphatic hydrocarbon group which may be bondedto the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms,more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbonatoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The cyclic hydrocarbon group for R¹⁰⁴ and R¹⁰⁵ may contain a heteroatom, such as a hetero ring. Specific examples includelactone-containing cyclic groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7), the —SO₂— containing cyclic grouprepresented by the aforementioned formulae (a5-r-1) to (a5-r-4), andother heterocyclic groups represented by chemical formulae (r-hr-1) to(r-hr-16) shown below.

Examples of the substituent for the cyclic group for R¹⁰⁴ and R¹⁰⁵include an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxy group, a carbonyl group, and a nitro group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The carbonyl group as the substituent is a group that substitutes amethylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Chain alkyl group which may have a substituent:

The chain alkyl group for R¹⁰⁴ and R¹⁰⁵ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, and still more preferably 1 to 10carbon atoms. Specific examples include a methyl group, an ethyl group,a propyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl group, adodecyl group, a tridecyl group, an isotridecyl group, a tetradecylgroup, a pentadecyl group, a hexadecyl group, an isohexadecyl group, aheptadecyl group, an octadecyl group, a nonadecyl group, an icosylgroup, a henicosyl group and a docosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15 carbon atoms, and still more preferably 3 to 10carbon atoms. Specific examples include a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group and a 4-methylpentyl group.

Chain Alkenyl Group which May have a Substituent:

The chain alkenyl group for R¹⁰⁴ and R¹⁰⁵ may be linear or branched, andpreferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbonatoms, still more preferably 2 to 4 carbon atoms, and most preferably 3carbon atoms. Examples of linear alkenyl groups include a vinyl group, apropenyl group (an allyl group) and a butynyl group. Examples ofbranched alkenyl groups include a 1-methylvinyl group, a 2-methylvinylgroup, a 1-methylpropenyl group and a 2-methylpropenyl group.

Among these examples, as the chain alkenyl group, a linear alkenyl groupis preferable, a vinyl group or a propenyl group is more preferable, anda vinyl group is most preferable.

As the substituent for the chain alkyl group or alkenyl group for R¹⁰⁴and R¹⁵, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group, an amino group, acyclic group for R¹⁰⁴ to R¹⁰⁵ may be mentioned.

Among these examples, as R¹⁰⁴ and R¹⁰⁵, a chain alkyl group which mayhave a substituent is preferable, and a linear or branched alkyl groupor a linear or branched fluorinated alkyl group is more preferable.

The chain alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. The smaller the number of carbon atoms of the chain alkyl groupfor R¹⁰⁴ and R¹⁰⁵, the more the solubility in a resist solvent isimproved. Further, in the chain alkenyl group for R¹⁰⁴ and R¹⁰⁵, thelarger the number of hydrogen atoms being substituted with fluorineatom(s), the stronger the acid becomes. The fluorination ratio of thechain alkyl group is preferably from 70 to 100%, more preferably from 90to 100%, and it is particularly desirable that the chain alkyl group bea perfluoroalkyl group in which all hydrogen atoms are substituted withfluorine atoms.

In formula (b-2), V¹⁰² and V¹⁰³ each independently represents a singlebond, an alkylene group or a fluorinated alkylene group, and is the sameas defined for V¹⁰¹ in formula (b-1).

In formula (b-2), L¹⁰¹ and L¹⁰² each independently represents a singlebond or an oxygen atom.

Anion Moiety of Component (b-3)

In formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent, andis the same as defined for R¹⁰¹ in formula (b-1).

L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—.

{Cation Moiety}

In formulae (b-1), (b-2) and (b-3), m represents an integer of 1 ormore, M′^(m+) represents an onium cation having a valency of m,preferably a sulfonium cation or an iodonium cation, and most preferablyan organic cation represented by any one of the following formulae(ca-1) to (ca-5).

In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² each independentlyrepresents an aryl group, an alkyl group or an alkenyl group, providedthat two of R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² may bemutually bonded to form a ring with the sulfur atom; R²⁰⁸ and R²⁰⁹ eachindependently represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; R²¹⁰ represents an aryl group which may have asubstituent, an alkyl group which may have a substituent, an alkenylgroup which may have a substituent, or an —SO₂— containing cyclic groupwhich may have a substituent; L²⁰¹ represents —C(═O)— or —C(═O)—O—; Y²⁰¹each independently represents an arylene group, an alkylene group or analkenylene group; x represents 1 or 2; and W²⁰¹ represents a linkinggroup having a valency of (x+1).

As the aryl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹², an unsubstituted arylgroup of 6 to 20 carbon atoms may be mentioned, and a phenyl group or anaphthyl group is preferable.

The alkyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² is preferably a chain orcyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² preferably has 2 to 10carbon atoms.

Specific examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,and groups represented by formulae (ca-r-1) to (ca-r-7) shown below.

In the formulae, each R′²⁰¹ independently represents a hydrogen atom, acyclic group which may have a substituent, a chain alkyl group which mayhave a substituent, or a chain alkenyl group which may have asubstituent.

As the cyclic group which may have a substituent, the chain alkyl groupwhich may have a substituent and the chain alkenyl group which may havea substituent for R′²⁰¹, the same groups as those described above forR¹⁰¹ may be mentioned. As the cyclic group which may have a substituentand chain alkyl group which may have a substituent, the same groups asthose described above for the acid dissociable group represented by theaforementioned formula (a1-r-2) may be also mentioned.

When R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹ and R²¹² are mutually bonded to forma ring with the sulfur atom, these groups may be mutually bonded via ahetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, ora functional group such as a carbonyl group, —SO—, —SO₂—, —SO₀₃—, —COO—,—CONH— or —N(RN)— (wherein RN represents an alkyl group of 1 to 5 carbonatoms). The ring containing the sulfur atom in the skeleton thereof ispreferably a 3 to 10-membered ring, and most preferably a 5 to7-membered ring. Specific examples of the ring formed include athiophene ring, a thiazole ring, a benzothiophene ring, a thianthrenering, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthenering, a thioxanthone ring, a phenoxathiin ring, a tetrahydrothiopheniumring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms, preferably a hydrogen atom or an alkylgroup of 1 to 3 carbon atoms, and when R²⁰⁸ and R²⁰⁹ each represents analkyl group, R²⁰⁸ and R²⁰⁹ may be mutually bonded to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or an —SO₂— containing cyclic group which may have asubstituent.

Examples of the aryl group for R²¹⁰ include an unsubstituted aryl groupof 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group for R²¹⁰, a chain or cyclic alkyl group having 1 to30 carbon atoms is preferable.

The alkenyl group for R²¹⁰ preferably has 2 to 10 carbon atoms.

The —SO₂— containing cyclic group for R²¹⁰ which may have a substituentis the same as defined for the —SO₂— containing cyclic group representedby any of the aforementioned general formulae (a5-r-1) to (a5-r-4).Among these examples, the “—SO₂— containing polycyclic group” ispreferable, and a group represented by general formula (a5-r-1) is morepreferable.

In formulae (ca-4) and (ca-5), each Y²⁰¹ independently represents anarylene group, an alkylene group or an alkenylene group.

Examples of the arylene group for Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group given as an example ofthe aromatic hydrocarbon group for R¹⁰¹ in the aforementioned formula(b-1).

Examples of the alkylene group and alkenylene group for Y²⁰¹ includegroups in which one hydrogen atom has been removed from the chain alkylgroup or the chain alkenyl group given as an example of R¹⁰¹ in theaforementioned formula (b-1).

In formulae (ca-4) and (ca-5), x represents 1 or 2.

W²⁰¹ represents a linking group having a valency of (x+1), i.e., adivalent or trivalent linking group.

As the divalent linking group for W²⁰¹, a divalent hydrocarbon groupwhich may have a substituent is preferable, and as examples thereof, thesame hydrocarbon groups (which may have a substituent) as thosedescribed above for Ya²¹ in the general formula (a2-1) may be mentioned.The divalent linking group for W²⁰¹ may be linear, branched or cyclic,and cyclic is more preferable. Among these, an arylene group having twocarbonyl groups, each bonded to the terminal thereof is preferable.Examples of the arylene group include a phenylene group and anaphthylene group, and a phenylene group is particularly desirable.

As the trivalent linking group for W²⁰¹, a group in which one hydrogenatom has been removed from the aforementioned divalent linking group forW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group may be mentioned. The trivalent linkinggroup for W²⁰¹ is preferably a group in which 2 carbonyl groups arebonded to an arylene group.

Specific examples of preferable cations represented by formula (ca-1)include cations represented by formulae (ca-1-1) to (ca-1-72) shownbelow.

In the formulae, g1, g2 and g3 represent recurring numbers, wherein g1is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is aninteger of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² may be mentioned.

Specific examples of preferable cations represented by the formula(ca-2) include a dihphenyliodonium cation and abis(4-tert-butylphenyl)iodonium cation.

Specific examples of preferable cations represented by formula (ca-3)include cations represented by formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of preferable cations represented by formula (ca-4)include cations represented by formulae (ca-4-1) and (ca-4-2) shownbelow.

Further, examples of preferable cations represented by formula (ca-5)include cations represented by formulae (ca-5-1) to (ca-5-3) shownbelow.

Among the above examples, as the cation moiety [(M′^(m+))_(l/m)], acation represented by general formula (ca-1) is preferable, and a cationrepresented by any one of formulae (ca-1-1) to (ca-1-72) is morepreferable.

In the resist composition of the present embodiment, the component (B1)preferably includes the component (b-1), more preferably at least onemember selected from the group consisting of a compound represented bygeneral formula (b-1-1) shown below (hereafter, sometimes referred to as“component (b-1-1)”), a compound represented by general formula (b-1-2)shown below (hereafter, sometimes referred to as “component (b-1-2)”), acompound represented by general formula (b-1-3) shown below (hereafter,sometimes referred to as “component (b-1-3)”), a compound represented bygeneral formula (b-1-4) shown below (hereafter, sometimes referred to as“component (b-1-4)”) and a compound represented by general formula(b-1-5) shown below (hereafter, sometimes referred to as “component(b-1-5)”), and still more preferably at least one member selected fromthe group consisting of the component (b-1-1), the component (b-1-4) andthe component (b-1-5).

In the formulae, R″¹⁰¹ to R″¹⁰⁴ each independently represents ahydrocarbon group containing an aromatic ring which may have asubstituent; each v″ independently represents an integer of 0 to 3; q″represents an integer of 1 to 20; each t″ independently represents aninteger of 1 to 3; and n″ represents 0 or 1.

In the formula, Rx⁵ and Rx⁶ each independently represents a hydrocarbongroup which may have a substituent or a hydrogen atom;

[Chemical Formula 61]

represents a double bond or a single bond; Rz¹ to Rz⁴ each independentlyrepresents, where valence allows, a hydrogen atom or a hydrocarbon groupwhich may have a substituent, or two or more of Rz¹ to Rz⁴ may bemutually bonded to form a ring structure; provided that at least one ofRx⁵, Rx⁶ and Rz¹ to Rz⁴ has an anionic group represented by generalformula (b1-r-an1) shown below, and the whole anion moiety is ann-valent anion; n represents an integer of 1 or more;

R⁰²¹ represents an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitrogroup;

n represents an integer of 1 to 3; n11 represents an integer of 0 to 8;

R⁰²² represents an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxy group, a carbonyl group or a nitrogroup;

n2 represents an integer of 1 to 3; and n21 represents an integer of 0to 8.

In the formula, R^(b01) represents a fluorinated alkyl group of 1 to 5carbon atoms or a fluorine atom; V^(b01) represents an alkylene group, afluorinated alkylene group or a single bond; and Y^(b10) represents adivalent linking group or a single bond.

In formulae (b-1-1) to (b-1-4), the hydrocarbon group containing anaromatic ring (which may have a substituent) represented by R″¹⁰¹ toR″¹⁰⁴ is preferably a group described above as an example of thehydrocarbon group containing an aromatic ring (which may have asubstituent) represented by R¹⁰¹, R¹⁰⁴ and R¹⁰⁶. The substituent is thesame as defined for the substituent for the aromatic ring in R¹⁰¹, R¹⁰⁴and R¹⁰⁶.

Among these examples, as R″¹⁰¹, a phenyl group which may have asubstituent or a naphthyl group which may have a substituent ispreferable.

Further, as R″¹⁰², a phenyl group which may have a substituent ispreferable.

In formula (b-1-5), Rx⁵ and Rx⁶ each independently represents ahydrocarbon group which may have a substituent or a hydrogen atom.

Rz¹ to Rz⁴ each independently represents, where valence allows, ahydrogen atom or a hydrocarbon group which may have a substituent, ortwo or more of Rz¹ to Rz⁴ may be mutually bonded to form a ringstructure.

The hydrocarbon group for Rx⁵, Rx⁶ and Rz¹ to Rz⁴ may be an aliphatichydrocarbon group or an aromatic hydrocarbon group, or may be a cyclichydrocarbon group or a chain hydrocarbon group.

Examples of the hydrocarbon group (which may have a substituent) forRx⁵, Rx⁶ and Rz¹ to Rz⁴ include a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent, or achain alkenyl group which may have a substituent.

Cyclic Group which May have a Substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group. An “aliphatic hydrocarbon group” refersto a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group may be either saturated or unsaturated, but ingeneral, the aliphatic hydrocarbon group is preferably saturated.Further, the cyclic hydrocarbon group for Rx⁵, Rx⁶ and Rz¹ to Rz⁴ maycontain a hetero atom, such as a hetero ring.

The aromatic hydrocarbon group as Rx⁵, Rx⁶, Rz¹ to Rz⁴ is a hydrocarbongroup having an aromatic ring. The aromatic hydrocarbon group preferablyhas 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, stillmore preferably 5 to 20 carbon atoms, still more preferably 6 to 15carbon atoms, and most preferably 6 to 10 carbon atoms. Here, the numberof carbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

In the aromatic hydrocarbon group for Rx⁵, Rx⁶ and Rz¹ to Rz⁴, specificexamples of the aromatic ring include benzene, naphthalene, anthracene,phenanthrene, biphenyl, or an aromatic heterocyclic ring in which partof the carbon atoms constituting any of these aromatic rings have beensubstituted with a hetero atom. Examples of the hetero atom within thearomatic hetero rings include an oxygen atom, a sulfur atom and anitrogen atom.

Specific examples of the aromatic hydrocarbon group for Rx⁵, Rx⁶ and Rz¹to Rz⁴ include a group in which one hydrogen atom has been removed fromthe aforementioned aromatic ring (an aryl group, such as a phenyl groupor a naphthyl group), and a group in which one hydrogen atom of theaforementioned aromatic ring has been substituted with an alkylene group(an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl groupor a 2-naphthylethyl group). The alkylene group (alkyl chain within thearylalkyl group) preferably has 1 to 4 carbon atom, more preferably 1 or2, and most preferably 1.

Examples of the cyclic aliphatic hydrocarbon group as Rx⁵, Rx⁶ and Rz¹to Rz⁴ include aliphatic hydrocarbon groups containing a ring in thestructure thereof.

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which one hydrogenatom has been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain aliphatic hydrocarbon group, and a group in whichthe alicyclic group is interposed within the aforementioned linear orbranched aliphatic hydrocarbon group, may be given.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which one or more hydrogen atoms have been removed from amonocycloalkane is preferable. The monocycloalkane preferably has 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. As the polycyclic alicyclic hydrocarbon group, a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane is preferable, and the polycyclic group preferably has 7to 30 carbon atoms. Among polycycloalkanes, a polycycloalkane having abridged ring polycyclic skeleton, such as adamantane, norbornane,isobomane, tricyclodecane or tetracyclodpdecane, and a polycycloalkanehaving a condensed ring polycyclic skeleton, such as a cyclic grouphaving a steroid skeleton are preferable.

Among these examples, as the cyclic aliphatic hydrocarbon group for Rx⁵,Rx⁶ and Rz¹ to Rz⁴, a group in which one or more hydrogen atoms havebeen removed from a monocycloalkane or a polycycloalkane is preferable,a group in which one hydrogen atom has been removed from amonocycloalkane is more preferable, and a group in which one hydrogenatom has been removed from cyclopentane or cyclohexane is still morepreferable.

The linear aliphatic hydrocarbon group which may be bonded to thealicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, morepreferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbonatoms, and most preferably 1 to 3 carbon atoms. As the linear aliphatichydrocarbon group, a linear alkylene group is preferable. Specificexamples thereof include a methylene group [—CH₂—], an ethylene group[—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group[—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group which may be bonded to thealicyclic hydrocarbon group preferably has 2 to 10 carbon atoms, morepreferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbonatoms, and most preferably 3 carbon atoms. As the branched aliphatichydrocarbon group, branched alkylene groups are preferred, and specificexamples include various alkylalkylene groups, including alkylmethylenegroups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—,—C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as—CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and—C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and—CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as—CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. As the alkyl group withinthe alkylalkylene group, a linear alkyl group of 1 to 5 carbon atoms ispreferable.

Further, examples of the cyclic group for Rx⁵, Rx⁶ and Rz¹ to Rz⁴ alsoinclude —COOR^(XYZ) and —OC(═O)R^(XYZ), wherein R^(XYZ) is alactone-containing cyclic group, a carbonate-containing cyclic group oran —SO₂-containing cyclic group.

Examples of the substituent for the cyclic group as Rx⁵˜Rx⁶, and Rz¹ toRz⁴ include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group, a nitro group and a carbonylgroup.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the aforementioned halogenated alkyl group includes a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The carbonyl group as the substituent is a group that substitutes amethylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Chain alkyl group which may have a substituent:

The chain alkyl group as Rx⁵, Rx⁶ and Rz¹ to Rz⁴ may be linear orbranched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, and still more preferably 1 to 10carbon atoms. Specific examples include a methyl group, an ethyl group,a propyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl group, adodecyl group, a tridecyl group, an isotridecyl group, a tetradecylgroup, a pentadecyl group, a hexadecyl group, an isohexadecyl group, aheptadecyl group, an octadecyl group, a nonadecyl group, an icosylgroup, a henicosyl group and a docosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15 carbon atoms, and still more preferably 3 to 10carbon atoms. Specific examples thereof include a 1-methylethyl group, a1,1-dimethylethyl group, a 1-methylpropyl group, a 2-methylpropyl group,a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentylgroup.

Chain alkenyl group which may have a substituent:

The chain alkenyl group for Rx⁵, Rx⁶ and Rz¹ to Rz⁴ may be linear orbranched, and preferably has 2 to 10 carbon atoms, more preferably 2 to5 carbon atoms, still more preferably 2 to 4 carbon atoms, and mostpreferably 3 carbon atoms. Examples of linear alkenyl groups include avinyl group, a propenyl group (an allyl group) and a butynyl group.

Examples of branched alkenyl groups include a 1-methylvinyl group, a2-methylvinyl group, a 1-methylpropenyl group and a 2-methylpropenylgroup.

Among these examples, as the chain alkenyl group, a linear alkenyl groupis preferable, a vinyl group or a propenyl group is more preferable, anda vinyl group is most preferable.

As the substituent for the chain alkyl group or alkenyl grouprepresented by Rx⁵, Rx⁶ and Rz¹ to Rz⁴ an alkoxy group, a halogen atom(such as a fluorine atom, a chlorine atom, a bromine atom or an iodineatom), a halogenated alkyl group, a hydroxy group, a carbonyl group, anitro group, an amino group, a cyclic group represented by Rx⁵, Rx⁶ andRz¹ to Rz⁴ may be mentioned.

Among these examples, as the hydrocarbon group for Rx⁵, Rx⁶ and Rz¹ toRz⁴, a cyclic group which may have a substituent or a chain alkyl groupwhich may have a substituent is preferable.

In formula (b-1-5), two of Rz¹ to Rz⁴ may be mutually bonded to form aring structure. For example, Rz¹ may form a ring structure with any ofRz² to Rz⁴. Specific examples of the ring structure include a ringstructure sharing one side of a six-membered ring in formula (bd1) (bondbetween a carbon atom to which Rz¹ and Rz² are bonded and a carbon atomto which Rz³ and Rz⁴ are bonded), a ring structure formed by bonding Rz¹and Rz², and a ring structure formed by bonding Rz³ and Rz⁴.

The ring structure formed by two or more of Rz¹ to Rz⁴ may be analicyclic hydrocarbon or an aromatic hydrocarbon, and is particularlypreferably an aromatic hydrocarbon.

Additionally, the ring structure may be a polycyclic structure composedof other ring structures.

The alicyclic hydrocarbon formed by two or more of Rz¹ to Rz⁴ may bepolycyclic or monocyclic. As a monocyclic alicyclic hydrocarbon, amonocycloalkane is preferable. The monocycloalkane preferably has 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. As a polycyclic alicyclic hydrocarbon, a polycycloalkane ispreferable. The polycycloalkane preferably has 7 to 30 carbon atoms.Specific examples of the polycycloalkane include a polycycloalkanehaving a polycyclic skeleton with a bridged ring, such as adamantane,norbomane, isobomane, tricyclodecane or tetracyclododecane; and apolycycloalkane having a polycyclic skeleton with a condensed ring, suchas a cyclic ring having a steroid skeleton.

It may be a heterocyclic structure in which a part of carbon atoms issubstituted with hetero atoms. A nitrogen-containing heterocyclic ringis particularly preferable, and specific examples thereof include cyclicimide and the like.

Examples of the aromatic hydrocarbon ring formed by two or more of Rz¹to Rz⁴ include benzene, fluorene, naphthalene, anthracene, phenanthrene,biphenyl, and an aromatic heterocyclic ring in which part of the carbonatoms constituting any of these aromatic rings have been substitutedwith a hetero atom.

The ring structure (alicyclic hydrocarbon, aromatic hydrocarbon) formedby Rz¹ to Rz⁴ may have a substituent. Examples of the substituentinclude the same substituents as those for the cyclic group as Rx¹ toRx⁴, Ry¹, Ry² and Rz¹ to Rz⁴ (for example, an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxyl group, anitro group, a carbonyl group, and the like).

Among the ring structures formed by two or more of Rz¹ to Rz⁴, a ringstructure sharing one side of a six-membered ring in formula (b-1-5)(bond between a carbon atom to which Rz¹ and Rz² are bonded and a carbonatom to which Rz³ and Rz⁴ are bonded) is preferable, and an aromaticring structure is more preferable in terms of diffusion controllabilityof an acid generated upon exposure.

In formula (b-1-5), the phase “where valence allows” is defined asfollows.

That is, in a case where a bond between a carbon atom to which Rz¹ andRz² are bonded and a carbon atom to which Rz³ and Rz⁴ are bonded is asingle bond, all of Rz¹, Rz², Rz³ and Rz⁴ are presents. In a case wherea bond between a carbon atom to which Rz¹ and Rz² are bonded and acarbon atom to which Rz³ and Rz⁴ are bonded is a double bond, only oneof Rz¹ and Rz², and only one of Rz³ and Rz⁴ are present. For example, ina case where Rz¹ and Rz³ are bonded to form an aromatic ring structure,Rz² and Rz⁴ are not present.

In formula (b-1-5), R⁰²¹ represents an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, a hydroxyl group, a carbonylgroup, and a nitro group.

The alkyl group as R⁰²¹ is preferably an alkyl group having 1 to 5carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as R⁰²¹ is preferably an alkoxy group having 1 to 5carbon atoms, more preferably a methoxy group, an ethoxy group, ann-propoxy group, an iso-propoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

The halogen atom as R⁰²¹ is preferably a fluorine atom, a chlorine atom,a bromine atom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group as R⁰²¹ include a group in whichsome or all hydrogen atoms in an alkyl group having 1 to 5 carbon atomssuch as a methyl group, an ethyl group, a propyl group, an n-butylgroup, or a tert-butyl group have been substituted with the halogenatoms.

In formula (b-1-5), n1 represents an integer of 1 to 3, preferably 1 or2, and more preferably 1.

In formula (b-1-5), n11 represents an integer of 0 to 8, preferably aninteger of 0 to 4, more preferably 0, 1 or 2, and still more preferably0 or 1.

In formula (b-1-5), R⁰²² represents an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, a hydroxy group, a carbonylgroup or a nitro group, and is the same as defined for R⁰²¹.

In formula (b-1-5), n2 represents an integer of 1 to 3, preferably 1 or2, and more preferably 1.

In formula (b-1-5), n21 represents an integer of 0 to 8, preferably aninteger of 0 to 4, more preferably 0, 1 or 2, and still more preferably0 or 1.

In formula (b-1-5), at least one of Rx⁵, Rx⁶ and Rz¹ to Rz⁴ has ananionic group represented by formula (b1-r-an1), and the whole anionmoiety is an n-valent anion; n represents an integer of 1 or more;

In formula (b1-r-an1), R^(b01) represents a fluorinated alkyl group of 1to 5 carbon atoms or a fluorine atom. R^(b01) is preferably aperfluoroalkyl group of 1 to 5 carbon atoms or a fluorine atom, and ismore preferably a fluorine atom.

In formula (b1-r-an1), V^(b01) represents an alkylene group, afluorinated alkylene group or a single bond.

The alkylene group or the fluorinated alkylene group for V^(b01)preferably has 1 to 4 carbon atoms, and more preferably 1 to 3 carbonatoms. Examples of the fluorinated alkyl group for V^(b01) include agroup in which part or all of the hydrogen atoms within an alkylenegroup have been substituted with fluorine. Among these examples, asV^(b01), an alkylene group having 1 to 4 carbon atoms, a fluorinatedalkylene group having 1 to 4 carbon atoms or a single bond ispreferable.

In formula (b1-r-an1), Y^(b10) represents a divalent linking group or asingle bond.

As the divalent linking group for Y^(b01), a divalent linking groupcontaining an oxygen atom may be given as a preferable example.

In the case where Y^(b10) is a divalent linking group containing anoxygen atom, Y^(b10) may contain an atom other than an oxygen atom.Examples of atoms other than an oxygen atom include a carbon atom, ahydrogen atom, a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—), a carbonyl group(—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations of theaforementioned non-hydrocarbon, hetero atom-containing linking groupswith an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto.

Examples of the divalent linking group containing an oxygen atom includedivalent linking groups represented by the aforementioned generalformulae (y-a1-1) to (y-a1-9).

Y^(b01) is preferably a divalent linking group containing an ether bondor a divalent linking group containing an ester bond, and groupsrepresented by the aforementioned formulas (y-a1-1) to (y-a1-6) arepreferable.

Specific examples of the anion group represented by formula (b1-r-an1)include:

in a case where Y^(b10) is a single bond, a fluorinated alkyl sulfonateanion such as —CH₂CF₂SO₃, —CF₂CF₂SO₃, trifluoromethane sulfonate anion,perfluorobutane sulfonate anion or the like.

in the case where Y^(b10) represents a divalent linking group containingan oxygen atom, anions represented by general formulae (b1-r-an11) to(b1-r-an13) shown below.

In the formulae, V″¹⁰¹ represents a single bond, an alkylene grouphaving 1 to 4 carbon atoms or a fluorinated alkylene group having 1 to 4carbon atoms; R¹⁰² represents a fluorine atom or a fluorinated alkylgroup having 1 to 5 carbon atoms; each v″ independently represents aninteger of 0 to 3; each q″ independently represents an integer of 1 to20; and n″ is 0 or 1.

In formulae (b1-r-an11) to (b1-r-an13), V″¹⁰¹ represents a single bond,an alkylene group having 1 to 4 carbon atoms, or a fluorinated alkylenegroup having 1 to 4 carbon atoms. V″¹⁰¹ is preferably a single bond, analkylene group having 1 carbon atom (methylene group), or a fluorinatedalkylene group having 1 to 3 carbon atoms.

In formulae (b1-r-an11) to (b1-r-an13), R¹⁰² represents a fluorine atomor a fluorinated alkyl group having 1 to 5 carbon atoms. R¹⁰² ispreferably a perfluoroalkyl group having 1 to 5 carbon atoms or afluorine atom, and more preferably a fluorine atom.

In general formulae (b1-r-an11) to (b1-r-an13), v″ represents an integerof 0 to 3, preferably 0 or 1.

q″ represents an integer of 1 to 20, preferably an integer of 1 to 10,more preferably an integer of 1 to 5, still more preferably 1, 2 or 3,and most preferably 1 or 2.

n″ is 0 or 1, preferably 0.

In the component (b-1-5), the number of anion group(s) may be 1 or 2,and is preferably 1.

In the component (b-1-5), the anion moiety as a whole forms an anionhaving a valency of n. n represents an integer of 1 or more; mrepresents an integer of 1 or more, preferably 1 or 2, and morepreferably 1.

Specific examples of preferable component (B1) are shown below.

In the resist composition of the present embodiment, as the component(B1), one kind of compound may be used, or two or more kinds ofcompounds may be used in combination.

In the resist composition of the present embodiment, the amount of thecomponent (B1) relative to 100 parts by weight of the component (A) ispreferably within a range from 0.1 to 100 parts by weight, morepreferably from 0.5 to 80 parts by weight, and still more preferablyfrom 1 to 60 parts by weight.

When the amount of the component (B1) is at least as large as the lowerlimit of the above-mentioned preferable range, in the formation of aresist pattern, various lithography properties such as sensitivity,resolution, LWR (line width roughness) and pattern shape are improved.On the other hand, when the amount of the component (B1) is no more thanthe upper limit of the above-mentioned range, film thickness loss of theresist pattern may be more reliably suppressed.

Component (B2)

The resist composition of the present embodiment may contain an acidgenerator other than the component (B1) (hereafter, referred to as“component (B2)”), as long as the effects of the present invention arenot impaired.

As the component (B2), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions may be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators.

As the onium salt acid generator, a compound represented by generalformula (b-1′) below (hereafter, sometimes referred to as “component(b-1′)”), a compound represented by general formula (b-2′) below(hereafter, sometimes referred to as “component (b-2′)”) or a compoundrepresented by general formula (b-3′) below (hereafter, sometimesreferred to as “component (b-3′)”) may be mentioned. The components(b-1′), (b-2′) and (b-3′) exclude compounds which fall under thedefinition of the aforementioned component (B1).

In the formulae, R³⁰¹ and R³⁰⁴ to R³⁰⁸ each independently represents acyclic group which may have a substituent, a chain alkyl group which mayhave a substituent or a chain alkenyl group which may have asubstituent, provided that R³⁰⁴ and R³⁰⁵ may be mutually bonded to forma ring;

R³⁰² represents a fluorine atom or a fluorinated alkyl group of 1 to 5carbon atoms; Y³⁰¹ represents a single bond or a divalent linking groupcontaining an oxygen atom; V³⁰¹ to V³⁰³ each independently represents asingle bond, an alkylene group or a fluorinated alkylene group; L³⁰¹ andL³⁰² each independently represents a single bond or an oxygen atom; L³⁰³to L³⁰⁵ each independently represents a single bond, —CO— or —SO₂—; mrepresents an integer of 1 or more; and M′^(m+) represents an m-valentonium cation.

{Anion Moiety}

Anion Moiety of Component (b-1′)

In formula (b-1′), R³⁰¹ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, and is the same as definedfor the a cyclic group which may have a substituent, a chain alkyl groupwhich may have a substituent or a chain alkenyl group which may have asubstituent for R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ in the aforementioned formulae (b-2)and (b-3).

As the substituent for the chain alkyl group or alkenyl group for R³⁰¹,an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, a carbonyl group, an amino group, a cyclic group for R¹⁰¹ or thelike may be used.

Among the above examples, as R³⁰¹, a cyclic group which may have asubstituent is preferable, and a cyclic hydrocarbon group which may havea substituent is more preferable. Specifically, a phenyl group, anaphthyl group, a group in which one or more hydrogen atoms have beenremoved from a polycycloalkane, a lactone-containing cyclic grouprepresented by any one of the aforementioned formula (a2-r-1), (a2-r-3)to (a2-r-7), and an —SO₂— containing cyclic group represented by any oneof the aforementioned formula (a5-r-1) to (a5-r-4).

In formula (b-1′), Y³⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

The divalent linking group containing an oxygen atom represented by Y³⁰¹is the same as defined for the divalent linking group containing anoxygen atom represented by Y¹⁰¹ in the aforementioned formula (b-1).

Y³⁰¹ is preferably a divalent linking group containing an ether bond ora divalent linking group containing an ester bond, and groupsrepresented by the aforementioned formulas (y-a1-1) to (y-a1-5) arepreferable.

In formula (b-1′), V³⁰¹ represents a single bond, an alkylene group or afluorinated alkylene group. The alkylene group and the fluorinatedalkylene group for V³⁰¹ are the same as defined for the alkylene groupand the fluorinated alkylene group for V¹⁰¹.

In formula (b-1′), R³⁰² represents a fluorine atom or a fluorinatedalkyl group of 1 to 5 carbon atoms. R³⁰² is preferably a fluorine atomor a perfluoroalkyl group having 1 to 5 carbon atoms, and morepreferably a fluorine atom.

Specific examples of the anion moiety of the component (b-1′) include:in the case where Y³⁰¹ is a single bond, a fluorinated alkylsulfonateanion, such as a trifluoromethanesulfonate anion or aperfluorobutanesulfonate anion; and in the case where Y³⁰¹ is a divalentlinking group containing an oxygen atom, an anion represented by any oneof formulae (an-1) to (an-3) shown below.

In the formulae, R″³⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any one of the aforementionedformulae (r-hr-1) to (r-hr-6), or a chain alkyl group which may have asubstituent: R″³⁰² represents an aliphatic cyclic group which may have asubstituent, a lactone-containing cyclic group represented by theaforementioned general formula (a2-r-1) and (a2-r-3) to (a2-r-7), or an—SO₂— containing cyclic group represented by any one of theaforementioned general formulae (a5-r-1) to (a5-r-4); R″³⁰³ representsan aromatic hydrocarbon group which may have a substituent, an aliphaticcyclic group which may have a substituent, or a chain alkenyl groupwhich may have a substituent; each v″ independently represents aninteger of 0 to 3; each q″ independently represents an integer of 1 to20; t″ represents an integer of 1 to 3; n″ represents 0 or 1.

As the aliphatic cyclic group (which may have a substituent) for R″³⁰¹,R″³⁰² and R″³⁰³, the same groups as the cyclic aliphatic hydrocarbongroup described above for R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ in the aforementionedformulae (b-2) and (b-3) are preferable. Examples of the substituentinclude the same substituents as those described above for the cyclicaliphatic hydrocarbon group for R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ in theaforementioned formulae (b-2) and (b-3) may be mentioned.

As the aromatic cyclic group (which may have a substituent) for R″³⁰³,the same groups as the aromatic hydrocarbon group described above forthe cyclic hydrocarbon group represented by R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ in theaforementioned formulae (b-2) and (b-3) are preferable. Examples of thesubstituent include the same substituents as those described above forthe cyclic aliphatic hydrocarbon group represented by R¹⁰⁵, R¹⁰⁷ andR¹⁰⁸ in the aforementioned formulae (b-2) and (b-3) may be mentioned.

As the chain alkyl group (which may have a substituent) for R″³⁰¹, thesame groups as those described above for the chain alkyl grouprepresented by R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸> in the aforementioned formulae (b-2)and (b-3) are preferable. As the chain alkenyl group (which may have asubstituent) represented by R″³⁰³, the same groups as those describedabove for the chain alkenyl group represented by R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ inthe aforementioned formulae (b-2) and (b-3) are preferable.

Anion Moiety of Component (b-2′)

In formula (b-2′), R³⁰⁴ and R³⁰⁵ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent, andis the same as defined for the a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent for R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ inthe aforementioned formulae (b-2) and (b-3). R³⁰⁴ and R³⁰⁵ may bemutually bonded to form a ring.

As R³⁰⁴ and R³⁰⁵, a chain alkyl group which may have a substituent ispreferable, and a linear or branched alkyl group or a linear or branchedfluorinated alkyl group is more preferable.

The chain alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. The smaller the number of carbon atoms of the chain alkyl groupfor R³⁰⁴ and R³⁰⁵, the more the solubility in a resist solvent isimproved. Further, in the chain alkenyl group for R³⁰⁴ and R³⁰⁵, thelarger the number of hydrogen atoms being substituted with fluorineatom(s), the stronger the acid becomes. The fluorination ratio of thechain alkyl group is preferably from 70 to 100%, more preferably from 90to 100%, and it is particularly desirable that the chain alkyl group bea perfluoroalkyl group in which all hydrogen atoms are substituted withfluorine atoms.

In formula (b-2′), V³⁰² and V³⁰³ each independently represents a singlebond, an alkylene group or a fluorinated alkylene group, and is the sameas defined for V¹⁰¹ in formula (b-1).

In formula (b-2′), L³⁰¹ and L³⁰² each independently represents a singlebond or an oxygen atom.

Anion Moiety of Component (b-3′)

In formula (b-3′), R³⁰⁶ to R³⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain alkyl group which may have asubstituent or a chain alkenyl group which may have a substituent, andis the same as defined for the a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent for R¹⁰⁵, R¹⁰⁷ and R¹⁰⁸ inthe aforementioned formulae (b-2) and (b-3).

L³⁰³ to L³⁰⁵ each independently represents a single bond, —CO— or —SO₂—.

{Cation Moiety}

In formulae (b-1′), (b-2′) and (b-3′), m represents an integer of 1 ormore, M′^(m+) represents an onium cation having a valency of m,preferably a sulfonium cation or an iodonium cation, and examplesthereof include an organic cation represented by any one of theaforementioned general formulae (ca-1) to (ca-5).

Specific examples of preferable cations represented by theaforementioned formula (ca-1) include cations represented by theaforementioned formulae (ca-1-1) to (ca-1-72) shown below.

Specific examples of preferable cations represented by theaforementioned formula (ca-2) include a diphenyliodonium cation and abis(4-tert-butylphenyl)iodonium cation.

Specific examples of preferable cations represented by theaforementioned formula (ca-3) include cations represented by theaforementioned formulae (ca-3-1) to (ca-3-6).

Specific examples of preferable cations represented by theaforementioned formula (ca-4) include cations represented by theaforementioned formulae (ca-4-1) and (ca-4-2).

Specific examples of preferable cations represented by theaforementioned formula (ca-5) include cations represented by theaforementioned formulae (ca-5-1) to (ca-5-3).

Among the above examples, as the cation moiety [(M′^(m+))_(l/m)], acation represented by general formula (ca-1) is preferable, and a cationrepresented by any one of formulae (ca-1-1) to (ca-1-72) is morepreferable.

In the resist composition of the present embodiment, as the component(B2), one kind of compound may be used, or two or more kinds ofcompounds may be used in combination.

When the resist composition contains the component (B2), the amount ofthe component (B2) relative to 100 parts by weight of the component (A)is preferably 50 parts by weight or less, more preferably 1 to 40 partsby weight, and still more preferably 5 to 30 parts by weight.

When the amount of the component (B2) is within the above-mentionedrange, the effect of using the component (B2) may be satisfactorilyachieved, and various lithography properties may be improved.

<Other Components>

The resist composition of the present embodiment may contain, inaddition to the aforementioned components (A) and (B), any othercomponents other than the components (A) and (B). Examples of the othercomponents include the components (D), (E), (F) and (S) described below.

<<Acid Diffusion Control Agent (D)>>

The resist composition according to the present embodiment may includean acid diffusion control agent component (hereafter, sometimes referredto as “component (D)”), in addition to the component (A), or in additionto the component (A) and the component (B). The component (D) functionsas an acid diffusion control agent, i.e., a quencher which traps theacid generated in the resist composition upon exposure.

The component (D) may be a photodecomposable base (D1) (hereafter,referred to as “component (D1)”) which is decomposed upon exposure andthen loses the ability of controlling of acid diffusion, or anitrogen-containing organic compound (D2) (hereafter, referred to as“component (D2)”) which does not fall under the definition of component(D1).

Component (D1)

When a resist pattern is formed using a resist composition containingthe component (D1), the contrast between exposed portions and unexposedportions of the resist film is improved.

The component (D1) is not particularly limited, as long as it isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion. As the component (D1), at least one compound selectedfrom the group consisting of a compound represented by general formula(d1-1) shown below (hereafter, referred to as “component (d1-1)”), acompound represented by general formula (d1-2) shown below (hereafter,referred to as “component (d1-2)”) and a compound represented by generalformula (d1-3) shown below (hereafter, referred to as “component(d1-3)”) is preferably used.

At exposed portions of the resist film, the components (d1-1) to (d1-3)are decomposed and then lose the ability of controlling of aciddiffusion (i.e., basicity), and therefore the components (d1-1) to(d1-3) cannot function as a quencher, whereas at unexposed portions, thecomponents (d1-1) to (d1-3) functions as a quencher.

In the formulae, Rd¹ to Rd⁴ represent a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, provided that, the carbonatom adjacent to the sulfur atom within the Rd² in the formula (d1-2)has no fluorine atom bonded thereto; Yd¹ represents a single bond or adivalent linking group; m represents an integer of 1 or more; and eachM^(m+) independently represents an organic cation having a valency of m.

{Component (d1-1)}

Anion Moiety

In formula (d1-1), Rd¹ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, and is the same groups asthose defined above for R¹⁰¹ in the aforementioned formula (b-1).

Among these, as the group for Rd¹, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain alkyl group which may have a substituent arepreferable. Examples of the substituent for these groups include ahydroxy group, an oxo group, an alkyl group, an aryl group, a fluorineatom, a fluorinated alkyl group, a lactone-containing cyclic grouprepresented by any one of the aforementioned formulae (a2-r-1) to(a2-r-7), an ether bond, an ester bond, and a combination thereof. Inthe case where an ether bond or an ester bond is included as thesubstituent, the substituent may be bonded via an alkylene group, and alinking group represented by any one of the aforementioned formulae(y-a1-1) to (y-a1-5) is preferable as the substituent.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbomane, isobomane, tricyclodecane or tetracyclododecane.

The chain alkyl group preferably has 1 to 10 carbon atoms, and specificexamples thereof include a linear alkyl group such as a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a nonyl or a decyl group, and abranched alkyl group such as a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup or a 4-methylpentyl group.

In the case where the chain alkyl group is a fluorinated alkyl grouphaving a fluorine atom or a fluorinated alkyl group, the fluorinatedalkyl group preferably has 1 to 11 carbon atoms, more preferably 1 to 8carbon atoms, and still more preferably 1 to 4 carbon atoms. Thefluorinated alkyl group may contain an atom other than fluorine.Examples of the atom other than fluorine include an oxygen atom, asulfur atom and a nitrogen atom.

As Rd¹, a fluorinated alkyl group in which part or all of the hydrogenatoms constituting a linear alkyl group have been substituted withfluorine atom(s) is preferable, and a fluorinated alkyl group in whichall of the hydrogen atoms constituting a linear alkyl group have beensubstituted with fluorine atoms (i.e., a linear perfluoroalkyl group) isparticularly desirable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

Cation Moiety

In formula (d1-1), M^(m+) represents an organic cation having a valencyof m.

As the organic cation for M^(m+), for example, the same cation moietiesas those represented by the aforementioned formulae (ca-1) to (ca-5) arepreferable, cation moieties represented by the aforementioned generalformulae (ca-1) is preferable, and cation moieties represented by theaforementioned formulae (ca-1-1) to (ca-1-72) are still more preferable.

As the component (d1-1), one kind of compound may be used, or two ormore kinds of compounds may be used in combination.

{Component (d1-2)}

Anion Moiety

In formula (d1-2), Rd² represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, and is the same groups asthose defined above for R¹⁰¹ in the aforementioned formula (b-1).

provided that, the carbon atom adjacent to the sulfur atom within Rd²group has no fluorine atom bonded thereto (i.e., the carbon atomadjacent to the sulfur atom within Rd² group does not substituted with afluorine atom). As a result, the anion of the component (d1-2) becomesan appropriately weak acid anion, thereby improving the quenchingability of the component (D).

As Rd², a chain alkyl group which may have a substituent or an aliphaticcyclic group which may have a substituent is preferable. The chain alkylgroup preferably has 1 to 10 carbon atoms, and more preferably 3 to 10carbon atoms. As the aliphatic cyclic group, a group in which one ormore hydrogen atoms have been removed from adamantane, norbomane,isobomane, tricyclodecane, tetracyclododecane or camphor (which may havea substituent) is more preferable.

The hydrocarbon group for Rd² may have a substituent. As thesubstituent, the same groups as those described above for substitutingthe hydrocarbon group (e.g., aromatic hydrocarbon group, aliphaticcyclic group, chain alkyl group) for Rd¹ in the formula (d1-1) may bementioned.

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

Cation Moiety

In formula (d1-2), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-2), one kind of compound may be used, or two ormore kinds of compounds may be used in combination.

{Component (d1-3)}

Anion Moiety

In formula (d1-3), Rd³ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, and is the same groups asthose defined above for R¹⁰¹ in the aforementioned formula (b-1), and acyclic group containing a fluorine atom, a chain alkyl group or a chainalkenyl group is preferable. Among these, a fluorinated alkyl group ispreferable, and more preferably the same fluorinated alkyl groups asthose described above for Rd¹.

In formula (d1-3), Rd⁴ represents a cyclic group which may have asubstituent, a chain alkyl group which may have a substituent or a chainalkenyl group which may have a substituent, and is the same groups asthose defined above for R¹⁰¹ in the aforementioned formula (b-1).

Among these, an alkyl group which may have substituent, an alkoxy groupwhich may have substituent, an alkenyl group which may have substituentor a cyclic group which may have substituent is preferable.

The alkyl group for Rd⁴ is preferably a linear or branched alkyl groupof 1 to 5 carbon atoms, and specific examples include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. Part of the hydrogen atoms within the alkyl groupfor Rd⁴ may be substituted with a hydroxy group, a cyano group or thelike.

The alkoxy group for Rd⁴ is preferably an alkoxy group of 1 to 5 carbonatoms, and specific examples thereof include a methoxy group, an ethoxygroup, an n-propoxy group, an iso-propoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group and an ethoxy group arepreferable.

As the alkenyl group for Rd⁴, the same groups as those described abovefor R¹⁰¹ in the aforementioned formula (b-1) may be mentioned, and avinyl group, a propenyl group (an allyl group), a 1-methylpropenyl groupand a 2-methylpropenyl group are preferable. These groups may have analkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to5 carbon atoms as a substituent.

As the cyclic group for Rd⁴, the same groups as those described abovefor R¹⁰¹ in the aforementioned formula (b-1) may be mentioned. Amongthese, as the cyclic group, an alicyclic group (e.g., a group in whichone or more hydrogen atoms have been removed from a cycloalkane such ascyclopentane, cyclohexane, adamantane, norbomane, isobomane,tricyclodecane or tetracyclododecane) or an aromatic group (e.g., aphenyl group or a naphthyl group) is preferable.

In formula (d1-3), Yd¹ represents a single bond or a divalent linkinggroup.

The divalent linking group for Yd¹ is not particularly limited, andexamples thereof include a divalent hydrocarbon group (aliphatichydrocarbon group, or aromatic hydrocarbon group) which may have asubstituent and a divalent linking group containing a hetero atom. Thedivalent linking groups are the same as defined for the divalenthydrocarbon group which may have a substituent and the divalent linkinggroup containing a hetero atom explained above as the divalent linkinggroup for Ya²¹ in the aforementioned formula (a2-1).

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylenegroup or a combination of these is preferable. As the alkylene group, alinear or branched alkylene group is more preferable, and a methylenegroup or an ethylene group is still more preferable.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

Cation Moiety

In formula (d1-3), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-3), one kind of compound may be used, or two ormore kinds of compounds may be used in combination.

As the component (D1), one kind of the aforementioned components (d1-1)to (d1-3), or at least two kinds of the aforementioned components (d1-1)to (d1-3) may be used in combination.

When the resist composition contains the component (D1), the amount ofthe component (D1) relative to 100 parts by weight of the component (A)is preferably within a range from 0.01 to 50 parts by weight, morepreferably from 0.05 to 40 parts by weight, and still more preferablyfrom 0.1 to 30 parts by weight.

When the amount of the component (D1) is at least as large as the lowerlimit of the above-mentioned preferable range, excellent lithographyproperties and excellent resist pattern shape may be more reliablyobtained. On the other hand, when the amount of the component (D1) is nomore than the upper limit of the above-mentioned preferable range, agood balance may be achieved with the other structural units, and thelithography properties may be improved.

Production Method of Component (D1):

The production methods of the components (d1-1) and (d1-2) are notparticularly limited, and the components (d1-1) and (d1-2) may beproduced by conventional methods.

Further, the production method of the component (d1-3) is notparticularly limited, and the component (d1-3) may be produced in thesame manner as disclosed in US2012-0149916.

Component (D2)

The acid diffusion control component may contain a nitrogen-containingorganic compound (D2) (hereafter, referred to as component (D2)) whichdoes not fall under the definition of component (D1).

The component (D2) is not particularly limited, as long as it functionsas an acid diffusion control agent, and does not fall under thedefinition of the component (D1). As the component (D2), any of theconventionally known compounds may be selected for use. Among these, analiphatic amine is preferable, and a secondary aliphatic amine ortertiary aliphatic amine is more preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine and tri-n-octylamine areparticularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1, 5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris {2-(2-methoxyethoxy)ethyl}amine,tris {2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris {2-(1-ethoxyethoxy)ethyl}amine,tris {2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole,indole, pyrazole, imidazole and derivatives thereof, as well astribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

As the component (D2), one type of compound may be used alone, or two ormore types may be used in combination.

When the resist composition contains the component (D2), the amount ofthe component (D2) is typically used in an amount within a range from0.01 to 5 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D2) is within theabove-mentioned preferable range, a good balance may be achieved withthe other structural units, and the lithography properties may beimproved.

<<At Least One Compound (E) Selected from the Group Consisting of anOrganic Carboxylic Acid, or a Phosphorus Oxo Acid or DerivativeThereof>>

In the resist composition of the present embodiment, for preventing anydeterioration in sensitivity, and improving the resist pattern shape andthe post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer, at least one compound (E)(hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof may be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

When the resist composition contains the component (E), the amount ofthe component (E) is typically used in an amount within a range from0.01 to 5 parts by weight, relative to 100 parts by weight of thecomponent (A).

<<Fluorine Additive (F)>>

In the present embodiment, the resist composition may further include afluorine additive (hereafter, referred to as “component (F)”) forimparting water repellency to the resist film, or improving lithographyproperties.

As the component (F), for example, a fluorine-containing polymericcompound described in Japanese Unexamined Patent Application, FirstPublication No. 2010-002870, Japanese Unexamined Patent Application,First Publication No. 2010-032994, Japanese Unexamined PatentApplication, First Publication No. 2010-277043, Japanese UnexaminedPatent Application, First Publication No. 2011-13569, and JapaneseUnexamined Patent Application, First Publication No. 2011-128226 may beused.

Specific examples of the component (F) include polymers having astructural unit (f1) represented by general formula (f1-1) shown below.As the polymer, a polymer (homopolymer) consisting of a structural unit(f1) represented by formula (f1-1) shown below; a copolymer of thestructural unit (f1) and a structural unit (a1) containing an aciddecomposable group that exhibits increased polarity by the action ofacid; and a copolymer of the structural unit (f1), a structural unitderived from acrylic acid or methacrylic acid and the structural unit(a1) are preferable. As the structural unit (a1) to be copolymerizedwith the structural unit (f1), a structural unit derived from1-ethyl-1-cyclooctyl (meth)acrylate or a structural unit derived from1-methyl-1-adamantyl (meth)acrylate is preferable.

In the formula, R is the same as defined above; Rf¹⁰² and Rf¹⁰³ eachindependently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms, or a halogenated alkyl group of 1 to 5 carbonatoms, provided that Rf¹⁰² and Rf¹⁰³ may be the same or different; nf¹represents an integer of 1 to 5; and Rf¹⁰¹ represents an organic groupcontaining a fluorine atom.

In formula (f1-1), R bonded to the carbon atom on the α-position is thesame as defined above. As R, a hydrogen atom or a methyl group ispreferable.

In formula (f1-1), examples of the halogen atom for Rf¹⁰² and Rf¹⁰³include a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable. Examples of thealkyl group of 1 to 5 carbon atoms for Rf¹⁰² and Rf¹⁰³ include the samealkyl group of 1 to 5 carbon atoms as those described above for R, and amethyl group or an ethyl group is preferable. Specific examples of thehalogenated alkyl group of 1 to 5 carbon atoms represented by Rf¹⁰² orRf¹⁰³ include groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is particularlydesirable. Among these examples, as Rf¹⁰² and Rf¹⁰³, a hydrogen atom, afluorine atom or an alkyl group of 1 to 5 carbon atoms is preferable,and a hydrogen atom, a fluorine atom, a methyl group or an ethyl groupis more preferable.

In formula (f1-1), nf¹ represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms within the hydrocarbon groupfluorinated, more preferably 50% or more, and most preferably 60% ormore, as the hydrophobicity of the resist film during immersion exposureis enhanced.

Among these, as Rf¹⁰¹, a fluorinated hydrocarbon group of 1 to 6 carbonatoms is preferable, and a trifluoromethyl group, —CH₂—CF₃,—CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ aremost preferable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and mostpreferably 10,000 to 30,000. When the Mw of the component (F) is no morethan the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the Mw is at least as large as the lower limit ofthe above-mentioned range, water repellency of the resist surfacebecomes satisfactory.

Further, the dispersity (Mw/Mn) of the component (F) is preferably 1.0to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

As the component (F), one type may be used alone, or two or more typesmay be used in combination.

When the resist composition contains the component (F), the component(F) is used in an amount within a range from 0.5 to 10 parts by weight,relative to 100 parts by weight of the component (A).

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, dissolution inhibitors, plasticizers, stabilizers,colorants, halation prevention agents, and dyes.

<<Organic Solvent (S)>>

The resist composition of the present embodiment may be prepared bydissolving the resist materials for the resist composition in an organicsolvent (hereafter, referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a homogeneous solution, and any organicsolvent may be appropriately selected from those which have beenconventionally known as solvents for a chemically amplified resistcomposition.

Examples of the component (S) include lactones such as γ-butyrolactone;ketones such as acetone, methyl ethyl ketone, cyclohexanone,methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone;polyhydric alcohols, such as ethylene glycol, diethylene glycol,propylene glycol and dipropylene glycol; compounds having an ester bond,such as ethylene glycol monoacetate, diethylene glycol monoacetate,propylene glycol monoacetate, and dipropylene glycol monoacetate;polyhydric alcohol derivatives including compounds having an ether bond,such as a monoalkylether (e.g., monomethylether, monoethylether,monopropylether or monobutylether) or monophenylether of any of thesepolyhydric alcohols or compounds having an ester bond (among these,propylene glycol monomethyl ether acetate (PGMEA) and propylene glycolmonomethyl ether (PGME) are preferable); cyclic ethers such as dioxane;esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

The component (S) may be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, γ-butyrolactone, EL and cyclohexanone arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent may be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL or cyclohexanone is mixed as the polar solvent,the PGMEA:EL or cyclohexanone weight ratio is preferably from 1:9 to9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME ismixed as the polar solvent, the PGMEA:PGME weight ratio is preferablyfrom 1:9 to 9:1, more preferably from 2:8 to 8:2, and still morepreferably 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME andcyclohexanone is also preferable.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate. In general, the component (S) is usedin an amount such that the solid content of the resist compositionbecomes within the range from 0.1 to 20% by weight, and preferably from0.2 to 10% by weight.

In the resist composition of the present embodiment, the component (A)includes a resin component (A1) having a structural unit (a0), and thecomponent (B) includes at least one member selected from the groupconsisting of a compound (b-1) represented by the aforementioned generalformula (b-1), a compound (b-2) represented by the aforementionedgeneral formula (b-2) and a compound (b-3) represented by theaforementioned general formula (b-3) (component (B1)).

In the resist composition of the present embodiment, both the component(A1) and the component (B1) have an aromatic ring in the structurethereof. Therefore, it is presumed that the interaction between thecomponent (A1) and the component (B1) is enhanced. As a result, it ispresumed that, in the formation of a resist pattern using a resistcomposition of the present embodiment, acid generated upon exposure maybe appropriately suppressed from being diffused to unexposed portions ofthe pattern (acid diffusion may be appropriately suppressed), and theroughness of the resist pattern may be improved.

(Method of Forming a Resist Pattern)

The method of forming a resist pattern according to the presentembodiment includes: forming a resist film on a substrate using a resistcomposition of the aforementioned embodiment; conducting exposure of theresist film; and developing the resist film to form a resist pattern.

The method for forming a resist pattern according to the presentembodiment may be performed, for example, as follows.

Firstly, a resist composition of the first aspect is applied to asubstrate using a spinner or the like, and a bake treatment (postapplied bake (PAB)) is conducted at a temperature of 80 to 150° C. for40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such an ArF exposureapparatus, an electron beam lithography apparatus or an EUV exposureapparatus, or by patterning via direct irradiation with an electron beamwithout using a mask pattern, baking treatment (post exposure baking(PEB)) is conducted under temperature conditions of 80 to 150° C. for 40to 120 seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment. Thedeveloping treatment is conducted using an alkali developing solution inthe case of an alkali developing process, and a developing solutioncontaining an organic solvent (organic developing solution) in the caseof a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin the case of an alkali developing process, and a rinse solutioncontaining an organic solvent in the case of a solvent developingprocess.

In the case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern may be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. If desired, bake treatment (post bake) may be conductedfollowing the developing.

In this manner, a resist pattern may be formed.

The substrate is not specifically limited and a conventionally knownsubstrate may be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereonmay be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) may be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method may be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness may be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film may be reduced, and anextremely fine pattern with a high aspect ratio may be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure may be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The resist composition is effective to KrF excimer laser, ArFexcimer laser, EB and EUV, and more effective to ArF excimer laser, EBand EUV, and most effective to EB and EUV.

The exposure of the resist film may be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure may be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) may be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents may be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, nitrile solvents, amide solvents and ether solvents, andhydrocarbon solvents.

A ketone solvent is an organic solvent containing C—C(═O)—C within thestructure thereof. An ester solvent is an organic solvent containingC—C(═O)—O—C within the structure thereof. An alcohol solvent is anorganic solvent containing an alcoholic hydroxy group in the structurethereof. An “alcoholic hydroxy group” refers to a hydroxy group bondedto a carbon atom of an aliphatic hydrocarbon group. A nitrile solvent isan organic solvent containing a nitrile group in the structure thereof.An amide solvent is an organic solvent containing an amide group withinthe structure thereof. An ether solvent is an organic solvent containingC—O—C within the structure thereof.

Some organic solvents have a plurality of the functional groups whichcharacterizes the aforementioned solvents within the structure thereof.In such a case, the organic solvent may be classified as any type of thesolvent having the characteristic functional group. For example,diethyleneglycol monomethylether may be classified as either an alcoholsolvent or an ether solvent.

A hydrocarbon solvent consists of a hydrocarbon which may behalogenated, and does not have any substituent other than a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

As the organic solvent contained in the organic developing solution,among these, a polar solvent is preferable, and ketone solvents, estersolvents and nitrile solvents are preferable.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone,2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethylketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone,diacetonylalcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone,isophorone, propylenecarbonate, γ-butyrolactone and methyl amyl ketone(2-heptanone). Among these examples, as a ketone solvent, methyl amylketone (2-heptanone) is preferable.

Examples of ester solvents include methyl acetate, butyl acetate, ethylacetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethylmethoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, ethylene glycolmonopropyl ether acetate, ethylene glycol monobutyl ether acetate,ethylene glycol monophenyl ether acetate, diethylene glycol monomethylether acetate, diethylene glycol monopropyl ether acetate, diethyleneglycol monoethyl ether acetate, diethylene glycol monophenyl etheracetate, diethylene glycol monobutyl ether acetate, diethylene glycolmonoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate,4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate,3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl etheracetate, propylene glycol monoethyl ether acetate, propylene glycolmonopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate,4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentylacetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate,3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate,4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methylformate, ethyl formate, butyl formate, propyl formate, ethyl lactate,butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butylcarbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butylpyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate,ethyl propionate, propyl propionate, isopropyl propionate, methyl2-hydroxypropionate, ethyl 2-hydroxypropionate,methyl-3-methoxypropionate, ethyl-3-methoxypropionate,ethyl-3-ethoxypropionate and propyl-3-methoxypropionate. Among theseexamples, as an ester solvent, butyl acetate is preferable.

Examples of nitrile solvents include acetonitrile, propionitrile,valeronitrile, and butyronitrile.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant may be used.

As the surfactant, a non-ionic surfactant is preferable, and a non-ionicfluorine surfactant or a non-ionic silicon surfactant is morepreferable.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment may be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinsetreatment after the developing treatment in the case of a solventdeveloping process, any of the aforementioned organic solvents containedin the organic developing solution may be used which hardly dissolvesthe resist pattern. In general, at least one solvent selected from thegroup consisting of hydrocarbon solvents, ketone solvents, estersolvents, alcohol solvents, amide solvents and ether solvents is used.Among these, at least one solvent selected from the group consisting ofhydrocarbon solvents, ketone solvents, ester solvents, alcohol solventsand amide solvents is preferable, more preferably at least one solventselected from the group consisting of alcohol solvents and estersolvents, and an alcohol solvent is particularly desirable.

The alcohol solvent used for the rinse liquid is preferably a monohydricalcohol of 6 to 8 carbon atoms, and the monohydric alcohol may belinear, branched or cyclic. Specific examples thereof include 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol, 4-octanol and benzyl alcohol. Among these,1-hexanol, 2-heptanol and 2-hexanol are preferable, and 1 hexanol and2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two ormore kinds of solvents may be used in combination. Further, an organicsolvent other than the aforementioned examples or water may be mixedtogether. However, in consideration of the development characteristics,the amount of water within the rinse liquid, based on the total amountof the rinse liquid is preferably 30% by weight or less, more preferably10% by weight or less, still more preferably 5% by weight or less, andmost preferably 3% by weight or less.

If desired, the rinse solution may have a conventional additive blended.Examples of the additive include surfactants. Examples of the additiveinclude surfactants. As the surfactant, the same surfactants as thosedescribed above may be mentioned, a non-ionic surfactant is preferable,and a non-ionic fluorine surfactant or a non-ionic silicon surfactant ismore preferable.

When a surfactant is added, the amount thereof based on the total amountof the rinse liquid is generally 0.001 to 5% by weight, preferably 0.005to 2% by weight, and more preferably 0.01 to 0.5% by weight.

The rinse treatment using a rinse liquid (washing treatment) may beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

In the method of forming a resist pattern according to the presentembodiment, since the resist composition according to the firstembodiment described above is used, sensitivity may be enhanced in theformation of a resist pattern. In addition, by the method of forming aresist pattern according to the present embodiment, lithographyproperties (resolution, reduction of roughness, and the like) may beimproved, and resolution may be enhanced. As a result, it becomespossible to form a resist pattern having a good shape.

Examples

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

Polymer Synthesis Example 1: Synthesis of Polymer P-1

10.0 g of monomer (m101), 12.7 g of monomer (m01) and 1.4 g ofdimethyl-2,2′-azobisisoutyrate (V-601) as a polymerization initiatorwere dissolved in 50.0 g of methyl ethyl ketone (MEK), followed bystirring in a nitrogen atmosphere at 85° C. for 5 hours. Then, to thereaction liquid was added 9.4 g of acetic acid and 160 g of methanol,followed by a deprotection reaction at 30° C. for 8 hours. After thereaction finished, the obtained reaction liquid was washed byprecipitating in 2,500 g of heptane. The obtained white solid wassubjected to filtration, followed by drying under reduced pressure overone night, so as to obtain 14.1 g of polymer P-1 as an objectivecompound.

With respect to the obtained polymer P-1, the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,600, and the dispersity was 1.63. Further, thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) as determined by ¹³C-NMRwas 1/m=50/50.

Polymer Synthesis Examples 2 to 5: Synthesis of Polymers P-2 to P-5

Using the compounds shown in Table 1 with the molar ratio indicated inTable 1, polymers P-2 to P-5 were synthesized in the same manner as inPolymer Synthesis Example 1.

With respect to the polymers P-2 to P-5, the compositional ratio of thepolymers (the molar ratio of the respective structural units in thepolymeric compound) as determined by ¹³C-NMR, the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) determined by thepolystyrene equivalent value as measured by GPC are also shown in Table1.

Polymer Synthesis Example 6: Synthesis of Polymer P-6

6.0 g of monomer (m101), 15.2 g of monomer (m01), 1.7 g of monomer (m21)and 1.4 g of dimethyl-2,2′-azobisisoutyrate (V-601) as a polymerizationinitiator were dissolved in 50.0 g of methyl ethyl ketone (MEK),followed by stirring in a nitrogen atmosphere at 85° C. for 5 hours.Then, to the reaction liquid was added 11.3 g of acetic acid and 190 gof methanol, followed by a deprotection reaction at 30° C. for 8 hours.After the reaction finished, the obtained reaction liquid was washed byprecipitating in 2,500 g of heptane. The obtained white solid wassubjected to filtration, followed by drying under reduced pressure overone night, so as to obtain 13.2 g of polymer (P-6) as an objectivecompound.

With respect to the polymer (P-6), the weight average molecular weight(Mw) and the polydispersity (Mw/Mn) were determined by the polystyreneequivalent value as measured by gel permeation chromatography (GPC). Asa result, it was found that the weight average molecular weight was7,200, and the polydispersity was 1.65. Further, the composition of thecopolymer (ratio (molar ratio) of the respective structural units withinthe structural formula) as determined by ¹³C-NMR was 1/m/n=30/60/10.

Polymer Synthesis Example 7: Synthesis of Polymer P-7

6.0 g of monomer (m101), 15.2 g of monomer (m01), 2.3 g of monomer (m31)and 1.4 g of dimethyl-2,2′-azobisisoutyrate (V-601) as a polymerizationinitiator were dissolved in 50.0 g of methyl ethyl ketone (MEK),followed by stirring in a nitrogen atmosphere at 85° C. for 5 hours.Then, to the reaction liquid was added 11.3 g of acetic acid and 190 gof methanol, followed by a deprotection reaction at 30° C. for 8 hours.After the reaction finished, the obtained reaction liquid was washed byprecipitating in 2,500 g of heptane. The obtained white solid wassubjected to filtration, followed by drying under reduced pressure overone night, so as to obtain 13.8 g of polymeric compound (P-7) as anobjective compound.

With respect to the polymer (P-7), the weight average molecular weight(Mw) and the polydispersity (Mw/Mn) were determined by the polystyreneequivalent value as measured by gel permeation chromatography (GPC). Asa result, it was found that the weight average molecular weight was7,000, and the polydispersity was 1.67. Further, as a result of ananalysis by carbon 13 nuclear magnetic resonance spectroscopy (150 MHz,¹³C-NMR), it was found that the composition of the copolymer (ratio(molar ratio) of the respective structural units within the structuralformula) was l/m/n=30/60/10.

Polymer Synthesis Examples 8 and 9: Synthesis of Polymers P-8 and P-9

Using the compounds shown in Table 1 with the molar ratio indicated inTable 1, polymers P-8 and P-9 were synthesized in the same manner as inPolymer Synthesis Example 1.

With respect to the polymers P-8 and P-9, the compositional ratio of thepolymers (the molar ratio of the respective structural units in thepolymeric compound) as determined by ¹³C-NMR, the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) determined by thepolystyrene equivalent value as measured by GPC are also shown in Table1.

Polymer Synthesis Example 10: Synthesis of Polymer P-10

Using the compounds shown in Table 1 with the molar ratio indicated inTable 1, polymer P-10 was synthesized in the same manner as in PolymerSynthesis Example 6.

With respect to the polymer P-10, the compositional ratio of thepolymers (the molar ratio of the respective structural units in thepolymeric compound) as determined by ¹³C-NMR, the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) determined by thepolystyrene equivalent value as measured by GPC are also shown in Table1.

Polymer Synthesis Example 11: Synthesis of Polymer P-11

Using the compounds shown in Table 1 with the molar ratio indicated inTable 1, polymer P-11 was synthesized in the same manner as in PolymerSynthesis Example 7.

With respect to the polymer P-11, the compositional ratio of thepolymers (the molar ratio of the respective structural units in thepolymeric compound) as determined by ¹³C-NMR, the weight averagemolecular weight (Mw) and the polydispersity (Mw/Mn) determined by thepolystyrene equivalent value as measured by GPC are also shown in Table1.

TABLE 1 Compositional ratio Structural unit (a0) Structural unit (a10)Structural unit (a1) Structural unit (a2) Structural unit (a3) RatioRatio Ratio Ratio Molecular Polymer Monomer (mol %) Monomer (mol %)Monomer (mol %) Monomer (mol %) weight Polydispersity P-1 (m101) 50(m01) 50 6600 1.63 P-2 (m101) 50 (m02) 50 6400 1.70 P-3 (m101) 50 (m03)50 6500 1.66 P-4 (m101) 50 (m04) 50 6800 1.68 P-5 (m101) 50 (m05) 506600 1.68 P-6 (m101) 30 (m01) 60 (m21) 10 7200 1.65 P-7 (m101) 30 (m01)60 (m31) 10 7000 1.67 P-8 (m101) 50 (m11) 50 6400 1.62 P-9 (m101) 50(m12) 50 6600 1.66 P-10 (m101) 30 (m11) 60 (m21) 10 7200 1.60 P-11(m101) 30 (m11) 60 (m31) 10 6800 1.61

<Production of Resist Composition>

The components shown in Tables 2 and 3 were mixed together and dissolvedto obtain each resist composition.

TABLE 2 Component Component Component Component (A) (B) (D) (S) Example1 (A)-1 (B)-1 (D)-1 (S)-1 [100] [13.5] [3.0] [8000] Example 2 (A)-1(B)-2 (D)-1 (S)-1 [100] [16.4] [3.0] [8000] Example 3 (A)-1 (B)-3 (D)-1(S)-1 [100] [16.9] [3.0] [8000] Example 4 (A)-1 (B)-4 (D)-1 (S)-1 [100][16.8] [3.0] [8000] Example 5 (A)-1 (B)-5 (D)-1 (S)-1 [100] [16.6] [3.0][8000] Example 6 (A)-1 (B)-6 (D)-1 (S)-1 [100] [23.0] [3.0] [8000]Example 7 (A)-1 (B)-7 (D)-1 (S)-1 [100] [14.8] [3.0] [8000] Example 8(A)-1 (B)-8 (D)-1 (S)-1 [100] [14.7] [3.0] [8000] Example 9 (A)-1 (B)-9(D)-1 (S)-1 [100] [15.2] [3.0] [8000] Example 10 (A)-1 (B)-10 (D)-1(S)-1 [100] [16.7] [3.0] [8000] Example 11 (A)-1 (B)-11 (D)-1 (S)-1[100] [16.3] [3.0] [8000] Example 12 (A)-1 (B)-12 (D)-1 (S)-1 [100][18.1] [3.0] [8000] Example 13 (A)-2 (B)-1 (D)-1 (S)-1 [100] [13.5][3.0] [8000] Example 14 (A)-3 (B)-1 (D)-1 (S)-1 [100] [13.5] [3.0][8000] Example 15 (A)-4 (B)-1 (D)-1 (S)-1 [100] [13.5] [3.0] [8000]Example 16 (A)-5 (B)-1 (D)-1 (S)-1 [100] [13.5] [3.0] [8000] Example 17(A)-6 (B)-1 (D)-1 (S)-1 [100] [13.5] [3.0] [8000] Example 18 (A)-7 (B)-1(D)-1 (S)-1 [100] [13.5] [3.0] [8000]

TABLE 3 Component Component Component Component (A) (B) (D) (S)Comparative (A)-1 (B)-13 (D)-1 (S)-1 Example 1 [100] [15.0] [3.0] [8000]Comparative (A)-1 (B)-14 (D)-1 (S)-1 Example 2 [100] [15.6] [3.0] [8000]Comparative (A)-1 (B)-15 (D)-1 (S)-1 Example 3 [100] [10.5] [3.0] [8000]Comparative (A)-2 (B)-14 (D)-1 (S)-1 Example 4 [100] [15.6] [3.0] [8000]Comparative (A)-1 (B)-16 (D)-1 (S)-1 Example 5 [100] [16.0] [3.0] [8000]Comparative (A)-1 (B)-17 (D)-1 (S)-1 Example 6 [100] [15.6] [3.0] [8000]Comparative (A)-1 (B)-18 (D)-1 (S)-1 Example 7 [100] [17.4] [3.0] [8000]Comparative (A)-8 (B)-1 (D)-1 (S)-1 Example 8 [100] [13.5] [3.0] [8000]Comparative (A)-9 (B)-1 (D)-1 (S)-1 Example 9 [100] [13.5] [3.0] [8000]Comparative (A)-10 (B)-1 (D)-1 (S)-1 Example 10 [100] [13.5] [3.0][8000] Comparative (A)-11 (B)-1 (D)-1 (S)-1 Example 11 [100] [13.5][3.0] [8000]

In Tables 2 and 3, the reference characters indicate the following. Thevalues in brackets [ ] indicate the amount (in terms of parts by weight)of the component added.

(A)-1 to (A)-1: the aforementioned polymers P-1 to P-11

(B)-1 to (B)-18: Acid generators represented by chemical formulae (B)-1to (B)-18 shown below

(D)-1: acid diffusion control agent represented by chemical formula(D)-1 below

(S)-1: a mixed solvent of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether=40/60 (weight ratio).

<Evaluation of Resist Composition>

Using the obtained resist compositions, resist patterns were formed, andevaluations of sensitivity (Eop), resolution and LWR were conducted asfollows.

[Formation of Resist Pattern]

Each of the resist compositions of examples and comparative examples wasapplied to a silicon substrate which had been treated withhexamethyldisilazane (HMDS) using a spinner, and was then prebaked (PAB)on a hot plate at 110° C. for 60 seconds and dried, thereby forming aresist film having a film thickness of 50 nm. A drawing (exposure) wascarried out on the resist film using an electron beam lithography systemJEOL-JBX-9300FS (manufactured by JEOL Ltd.) with acceleration voltage of100 kV and a target size of 1:1 line-and-space pattern (line width: 50nm) (hereinafter referred to as an “LS pattern”). Then, a post exposurebake (PEB) treatment was conducted at 110° C. for 60 seconds.

Thereafter, alkali developing was conducted for 60 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.). Then, water rinsing was conducted for 15 seconds using purewater. As a result, a 1:1 LS pattern having a line width of 50 nm wasformed.

[Evaluation of Optimum Exposure Dose (Eop)]

The optimum exposure dose Eop (μC/cm²) with which the LS pattern wasformed in the above formation of resist pattern was determined. Theresults are shown in Tables 4 and 5.

[Evaluation of Resolution]

The critical resolution (nm) with the above Eop was determined using ascanning electron microscope (product name: S-9380, manufactured byHitachi High-Technologies Corporation). Specifically, the exposure dosewas gradually increased from the optimum exposure dose Eop, and theminimum size of the pattern which resolves without collapse (fall) wasdetermined. The results are shown in Tables 4 and 5.

[Evaluation of Line Width Roughness (LWR)]

With respect to the LS pattern formed in the above “formation of resistpattern”, 30 was determined as a yardstick for indicating LWR. “30”indicates a value of 3 times the standard deviation (o) (i.e., 30)(unit: nm) determined by measuring the line positions at 400 points inthe lengthwise direction of the line using a scanning electronmicroscope (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation; acceleration voltage: 800V). The resultsare shown in Tables 4 and 5. The smaller this 30 value is, the lower thelevel of roughness on the side walls of the line, indicating that an LSpattern with a uniform width was obtained.

TABLE 4 Eop Resolution LWR (μC/cm²) (nm) (nm) Example 1 85 28 4.9Example 2 85 28 4.6 Example 3 85 28 4.4 Example 4 85 28 4.2 Example 5 8528 4.1 Example 6 85 32 5.1 Example 7 85 28 4.4 Example 8 85 28 4.8Example 9 85 28 4.7 Example 10 85 28 4.5 Example 11 85 28 4.4 Example 1280 24 4.5 Example 13 90 28 4.9 Example 14 80 24 4.6 Example 15 75 24 4.4Example 16 80 28 4.5 Example 17 95 28 4.6 Example 18 100 28 4.4

TABLE 5 Eop Resolution LWR (μC/cm²) (nm) (nm) Comparative 100 40 5.6Example 1 Comparative 100 40 5.9 Example 2 Comparative 100 50 6.0Example 3 Comparative 105 40 6.1 Example 4 Comparative 95 40 5.8 Example5 Comparative 95 40 5.7 Example 6 Comparative 90 36 5.8 Example 7Comparative 90 36 5.6 Example 8 Comparative 90 36 5.8 Example 9Comparative 100 36 5.3 Example 10 Comparative 105 36 5.2 Example 11

From the results shown in Tables 5 and 6, it was confirmed that theresist compositions of Examples 1 to 18 exhibited good sensitivity,resolution and LWR, as explained below.

The resist composition of Comparative Examples 1 to 4 have the sameformulations as those of the resist compositions of Examples 1 to 9,except that a compound represented by formula (b-1) in which R¹⁰¹ is nota hydrocarbon group containing an aromatic ring which may have asubstituent was used as the component (B). It was confirmed that theresist compositions of Examples 1 to 9 exhibited improved sensitivity,resolution and LWR as compared to the resist compositions of ComparativeExamples 1 to 4.

The resist composition of Comparative Examples 5 to 7 have the sameformulations as those of the resist compositions of Examples 10 to 12,except that a compound represented by formula (b-1) in which R¹⁰¹ is nota hydrocarbon group containing an aromatic ring which may have asubstituent was used as the component (B). It was confirmed that theresist compositions of Examples 10 to 12 exhibited improved sensitivity,resolution and LWR as compared to the resist compositions of ComparativeExamples 5 to 7.

Further, it was confirmed that the resist compositions of Examples 1 and13 to 16 exhibited improved resolution and LWR as compared to the resistcompositions of Comparative Examples 8 and 9 which have the sameformulations as those of the resist compositions of Examples 1 and 13 to16, except for the component (A). It was also confirmed that the resistcompositions of Examples 1 and 13 to 16 exhibited the same level ofsensitivity as the resist compositions of Comparative Examples 8 and 9.

The resist composition of Comparative Examples 8 and 9 have the sameformulations as those of the resist compositions of Examples 1 and 13,except that a polymer in which the structural unit (a0) has beenreplaced by a corresponding structural unit was used as the component(A). It was confirmed that the resist compositions of Examples 1 to 13exhibited improved resolution and LWR as compared to the resistcompositions of Comparative Examples 8 and 9. It was also confirmed thatthe resist compositions of Examples 1 and 13 exhibited the same level ofsensitivity as the resist compositions of Comparative Examples 8 and 9.

The resist composition of Comparative Examples 10 and 11 have the sameformulations as those of the resist compositions of Examples 17 and 18,except that a polymer in which the structural unit (a0) has beenreplaced by a corresponding structural unit was used as the component(A). It was confirmed that the resist compositions of Examples 17 and 18exhibited improved sensitivity, resolution and LWR as compared to theresist compositions of Comparative Examples 10 and 11.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, the resist composition comprising: a base component (A)which exhibits changed solubility m a developing solution under actionof acid, and an acid generator component (B) which generates acid uponexposure, the base component (A) comprising a resin component (A1)comprising a structural unit (a0) represented by general formula (a0)shown below, and the acid generator component (B) comprising at leastone member selected from the group consisting of a compound (b-1)represented by general formula (b-1) shown below, a compound (b-2)represented by general formula (b-2) shown below and a compound (b-3)represented by general formula (b-3) shown below:

wherein R⁰ represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va^(x0)represents a single bond or a divalent linking group; Wa is a divalentaromatic hydrocarbon group represented by the formula:

wherein *1 represents a bonding site to which Va^(x0) is bonded, and *2represents a bonding site to which —C(═O)—O (-Va⁰-C(═O)—O—_(na0)-Ra⁰⁰ isbonded, provided that a hydrogen atom bonded to the benzene ring in thedivalent aromatic hydrocarbon group represented by the above formula maybe substituted with a substituent; Va⁰ represents a divalent hydrocarbongroup which may have an ether bond; n_(a0) represents an integer of 0 to2; and Ra⁰⁰ is a group represented by general formula (a1-r2-1) shownbelow, a group represented by general formula (a1-r2-2) shown below, agroup represented by general formula (a1-r2-3) shown below or a grouprepresented by general formula (a1-r2-4) shown below:

wherein Ra′¹⁰ represents an alkyl group having 1 to 10 carbon atoms;Ra′¹¹ is a group which forms an aliphatic cyclic group together with acarbon atom having Ra′¹⁰ bonded thereto, or a fused cyclic group inwhich an aromatic ring is fused with the alicyclic group; Ya representsa carbon atom; Xa represents a group which forms a monocyclic aliphatichydrocarbon group together with Ya, provided that part or all of thehydrogen atoms of the monocyclic aliphatic hydrocarbon group may besubstituted; Ra⁰¹ to Ra⁰³ each independently represents a hydrogen atom,a monovalent saturated chain hydrocarbon group of 1 to 10 carbon atomsor a monovalent saturated aliphatic cyclic hydrocarbon group of 3 to 20carbon atoms, provided that part or all of the hydrogen atoms of thesaturated chain hydrocarbon or the saturated aliphatic cyclichydrocarbon may be substituted; two or more of Ra⁰¹ to Ra⁰³ may bemutually bonded to form a cyclic structure; Yaa represents a carbonatom; Xaa represents a group which forms an aliphatic cyclic grouptogether with Yaa; Ra⁰⁴ represents an aromatic hydrocarbon group whichmay have a substituent; Ra′¹² and Ra′¹³ each independently represent amonovalent chain saturated hydrocarbon group having 1 to 10 carbonatoms, provided that part or all of the hydrogen atoms of the saturatedhydrocarbon group may be substituted; Ra′¹⁴ represents an aromatichydrocarbon group which may have a hydrogen atom substituted with asubstituent; and * represents a bonding site;

wherein R¹⁰¹, R¹⁰⁴ and R¹⁰⁶ each independently represents a hydrocarbongroup containing an aromatic ring which may have a substituent; R¹⁰⁵,R¹⁰⁷ and R¹⁰⁸ each independently represents a cyclic group which mayhave a substituent, a chain alkyl group which may have a substituent ora chain alkenyl group which may have a substituent; R¹⁰² represents afluorine atom or a fluorinated alkyl group of 1 to 5 carbon atoms; Y¹⁰¹represents a single bond or a divalent linking group containing anoxygen atom; V¹⁰¹ to V¹⁰³ each independently represents a single bond,an alkylene group or a fluorinated alkylene group; L¹⁰¹ and L¹⁰² eachindependently represents a single bond or an oxygen atom; L¹⁰³ and L¹⁰⁵each independently represents a single bond, —CO— or —SO₂—; m representsan integer of 1 or more; and M′^(m+) represents an m-valent oniumcation.
 2. The resist composition according to claim 1, wherein theresin component (A1) further comprises a structural unit (a10)represented by general formula (a10-1) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ya^(x1)represents a single bond or a divalent linking group; Wa^(x1) representsan aromatic hydrocarbon group having a valency of (n_(ax1)+1); andn_(ax1) represents an integer of 1 or more.
 3. A method of forming aresist pattern, comprising: forming a resist film on a substrate using aresist composition according to claim 1; exposing the resist film; anddeveloping the exposed resist film to form a resist pattern.
 4. Theresist pattern forming method according to claim 3, wherein the resistfilm is exposed with extreme ultraviolet (EUV) or electron beam (EB). 5.A resist composition which generates acid upon exposure and exhibitschanged solubility in a developing solution under action of acid, theresist composition comprising: a base component (A) which exhibitschanged solubility in a developing solution under action of acid, and anacid generator component (B) which generates acid upon exposure, thebase component (A) comprising a resin component (A1) comprising astructural unit (a0) represented by general formula (a0) shown below,and the acid generator component (B) comprising at least one memberselected from the group consisting of a compound (b-1) represented bygeneral formula (b-1) shown below, a compound (b-2) represented bygeneral formula (b-2) shown below and a compound (b-3) represented bygeneral formula (b-3) shown below:

wherein R⁰ represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va^(x0)represents a single bond or a divalent linking group; Wa represents agroup in which two hydrogen atoms have been removed from benzene,naphthalene, anthracene, phenanthrene, pyridine, thiophene, biphenyl orfluorene, provided that Wa may have a hydrogen atom substituted with alinear or branched alkyl group having 1 to 5 carbon atoms, a halogenatom, or a linear or branched halogenated alkyl group having 1 to 5carbon atoms; Va⁰ represents a divalent hydrocarbon group which may havean ether bond; n_(a0) represents an integer of 0 to 2; and Ra⁰⁰ is agroup represented by general formula (a1-r2-1) shown below, a grouprepresented by general formula (a1-r2-2) shown below, a grouprepresented by general formula (a1-r2-3) shown below or a grouprepresented by general formula (a1-r2-4) shown below:

wherein Ra′¹⁰ represents an alkyl group having 1 to 10 carbon atoms;Ra′¹¹ is a group which forms an aliphatic cyclic group together with acarbon atom having Ra′¹⁰ bonded thereto, or a fused cyclic group inwhich an aromatic ring is fused with the alicyclic group; Ya representsa carbon atom; Xa represents a group which forms a monocyclic aliphatichydrocarbon group together with Ya, provided that part or all of thehydrogen atoms of the monocyclic aliphatic hydrocarbon group may besubstituted; Ra⁰¹ to Ra⁰³ each independently represents a hydrogen atom,a monovalent saturated chain hydrocarbon group of 1 to 10 carbon atomsor a monovalent saturated aliphatic cyclic hydrocarbon group of 3 to 20carbon atoms, provided that part or all of the hydrogen atoms of thesaturated chain hydrocarbon or the saturated aliphatic cyclichydrocarbon may be substituted; two or more of Ra⁰¹ to Ra⁰³ may bemutually bonded to form a cyclic structure; Yaa represents a carbonatom; Xaa represents a group which forms an aliphatic cyclic grouptogether with Yaa; Ra⁰⁴ represents an aromatic hydrocarbon group whichmay have a substituent; Ra′¹² and Ra′¹³ each independently represent amonovalent chain saturated hydrocarbon group having 1 to 10 carbonatoms, provided that part or all of the hydrogen atoms of the saturatedhydrocarbon group may be substituted; Ra′ ¹⁴ represents an aromatichydrocarbon group which may have a hydrogen atom substituted with asubstituent; and * represents a bonding site;

wherein R¹⁰¹, R¹⁰⁴ and R¹⁰⁶ each independently represents a hydrocarbongroup containing an aromatic ring which may have a substituent; R¹⁰⁵,R¹⁰⁷ and R¹⁰⁸ each independently represents a cyclic group which mayhave a substituent, a chain alkyl group which may have a substituent ora chain alkenyl group which may have a substituent; R¹⁰² represents afluorine atom or a fluorinated alkyl group of 1 to 5 carbon atoms; Y¹⁰¹represents a single bond or a divalent linking group containing anoxygen atom; V¹⁰¹ to V¹⁰³ each independently represents a single bond,an alkylene group or a fluorinated alkylene group; L¹⁰¹ and L¹⁰² eachindependently represents a single bond or an oxygen atom; L¹⁰³ to L¹⁰⁵each independently represents a single bond, —CO— or —SO₂—; m representsan integer of 1 or more; and M′^(m+) represents an m-valent oniumcation.